Cyrille Kossigan Kokou-Kpolou

Charlemagne Simplice Moukouta

Joanic Masson

Amal Bernoussi

Jude Mary Cénat

Marie-Frédérique Bacqué

Correlates of grief-related disorders and mental health outcomes among adult refugees exposed to trauma and bereavement: A systematic review and future research directions

Keywords: Bereavement Trauma Grief-related disorders Immigrant, refugee, asylum seeker Psychopathology

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Introduction

Although the fields of trauma and bereavement are connected [START_REF] Green | Traumatic loss: conceptual and empirical links between trauma and bereavement[END_REF]Figley et al., 1997;[START_REF] Raphael | The interaction of trauma and grief[END_REF][START_REF] Regehr | Intersections between grief and trauma: toward an empirically based model for treating traumatic grief[END_REF][START_REF] Stroebe | The traumatization of grief? A conceptual framework for understanding the trauma-bereavement interface[END_REF], research on psychopathology among immigrants and refugees has mainly emphasized trauma, its aftermath (posttraumatic stress disorder [PTSD], depression, anxiety) and its contributing factors. Much of the research has demonstrated that refugees are at high risk for PTSD, with [START_REF] Fazel | Prevalence of serious mental disorder in 7000 refugees resettled in western countries: a systematic review[END_REF] estimating this risk to be 10 times higher for adult refugees resettled in Western countries compared to an age-matched general population. This heightened risk is associated with multiple traumatic events, including acts of violence, threats of death, disappearance or loss of loved ones, witnessing death, and postmigration stressors [START_REF] Aoun | Post-traumatic stress disorder symptoms and associated risk factors: a cross-sectional study among Syrian refugees[END_REF][START_REF] Chen | Pre-migration and post-migration factors associated with mental health in humanitarian migrants in Australia and the moderation effect of post-migration stressors: findings from the first wave data of the BNLA cohort study[END_REF][START_REF] Knipscheer | Trauma exposure and refugee status as predictors of mental health outcomes in treatmentseeking refugees[END_REF][START_REF] Tufan | Post-traumatic stress disorder among asylum seekers and refugees in Istanbul may be predicted by torture and loss due to violence[END_REF]. Notably, [START_REF] Tufan | Post-traumatic stress disorder among asylum seekers and refugees in Istanbul may be predicted by torture and loss due to violence[END_REF] demonstrated that suffering from torture and from the death of significant others due to violence highly predicted PTSD in asylum seekers and refugees in Istanbul, Turkey. Trauma and bereavement are not mutually exclusive but often coincide among immigrants and refugees [START_REF] Claycomb | Persistent complex bereavement disorder symptom domains relate differentially to PTSD and depression: a study of war-exposed Bosnian adolescents[END_REF][START_REF] Heus | Day patient treatment for traumatic grief: preliminary evaluation of a one-year treatment programme for patients with multiple and traumatic losses[END_REF][START_REF] Regehr | Intersections between grief and trauma: toward an empirically based model for treating traumatic grief[END_REF].

Findings from literature reviews [START_REF] Chan | Well-being after trauma: a review of posttraumatic growth among refugees[END_REF][START_REF] Siriwardhana | A systematic review of resilience and mental health outcomes of conflict-driven adult forced migrants[END_REF][START_REF] Xu | How resilient a refugee community could be: the Vietnamese of New Orleans[END_REF] have shown that a majority of refugees recover or demonstrate resilience from exposure to trauma and multiple deaths. Family and community support, feelings of belonging to the same community, supportive relationships, and religious beliefs may enhance personal resilience capacities and coping responses, which, in turn, may predict better mental health and posttraumatic growth. However, an unknown proportion of refugees may be at risk for chronic or pathological grief and may experience clinically significant difficulties in adjusting to the death of loved ones. In addition, risk and vulnerability factors associated with pathological grief remain relatively unknown across the literature on bereaved refugee populations. The current review sought to update the empirical knowledge on this issue with critical regard to the present conceptualization of pathological grief.

Formerly known as ʻtraumatic grief' or ʻcomplicated grief', pathological grief has recently been conceptualized as a distinct mental disorder. This pathological condition has been introduced in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a provisional diagnostic category called "Persistent Complex Bereavement Disorder" (PCBD; American Psychiatric Association [APA], 2013). Additionally, the World Health Organization (2018) has moved toward a similar diagnostic category in the 11th edition of the International Classification of Diseases (ICD-11), which is called "Prolonged Grief Disorder" (PGD). The two grief-related disorders (PCBD and PGD) involve maladaptive grief reactions such as separation distress (e.g., intense yearning and longing for the deceased) and reactive painful and uncontrollable emotions (e.g., bitterness or anger, numbness) [START_REF] Boelen | Disturbed grief: prolonged grief disorder and persistent complex bereavement disorder[END_REF][START_REF] Maciejewski | Prolonged grief disorder" and "persistent complex bereavement disorder", but not "complicated grief", are one and the same diagnostic entity: an analysis of data from the Yale bereavement study[END_REF][START_REF] Maciejewski | Prolonged, but not complicated, grief is a mental disorder[END_REF].

Beyond their semantic nuances, both grief diagnostic constructs may diverge in their predictive and concurrent validity. In a recent factor-analytic study, [START_REF] Boelen | Evaluation of the factor structure, prevalence, and validity of disturbed grief in DSM-5 and ICD-11[END_REF] found that meeting PCBD criteria was associated with higher levels of depression and total PTSD symptoms than meeting PGD criteria, particularly PTSD-avoidance and PTSD-hyperarousal (but not PTSD-intrusions) one year after the death of a loved one. The fact that PCBD symptoms emerged as unrelated to PTSD-intrusions seems less surprising considering that the study sample predominantly comprised individuals who had lost a loved one due to natural causes of death (86.7%) among the general community. Seemingly, PTSD-intrusions wear off quicker among those bereaving natural deaths than among those bereaving violent deaths. The latter type of deaths is frequently related to distressing reminders. An alternative explanation is that mourners mobilize efforts to avoid intrusive thoughts and images or any external reminders linked to the lost person. For instance, in their study of war-bereaved Bosnian adolescents, [START_REF] Claycomb | Persistent complex bereavement disorder symptom domains relate differentially to PTSD and depression: a study of war-exposed Bosnian adolescents[END_REF] reported a strong correlation between PCBD symptoms and PTSD-avoidance. It remains unclear whether pathological grief (PCBD in particular, as currently conceptualized) is essentially distinct from PTSD, or whether it combines pathological grief and PTSD, as well as how both converge and interfere with each other. Nonetheless, these findings challenged the conceptualization of both diagnostic constructs and their competing criteria sets. It could be asked, in line with [START_REF] Lane | Refugees, grief and loss: critical debates [online[END_REF] see also [START_REF] Bacqué | Deuils et traumatismes [Bereavements and traumatisms[END_REF], whether grief reactions among traumatically bereaved populations should fall within the normative framework of trauma or within pathological grief.

The Multidimensional Grief Theory (MGT) could posit as a suitable theoretical framework for examining boundaries between responses to bereavement and responses to trauma. It has been framed as a developmental lifespan theory of bereavement-related risk and resilience factors [START_REF] Kaplow | Using multidimensional grief theory to explore the effects of deployment, reintegration, and death on military youth and families[END_REF][START_REF] Kaplow | Persistent complex bereavement disorder as a call to action: using a proposed DSM-5 diagnosis to advance the field of childhood grief[END_REF]Layne et al., 2017a). It relies on the recently proposed DSM-5 PCBD model and conceptually bridges item responses to bereavement and trauma in more detail. In fact, the PCBD is intended to be multidimensional by capturing separation distress, reactive distress including circumstance-related distress, and disruption in personal and social identity. Its diagnostic criteria, compared to those currently proposed by PGD which prioritize flexibility for clinical utility and international applicability [START_REF] Killikelly | Prolonged grief disorder for ICD-11: the primacy of clinical utility and international applicability[END_REF][START_REF] Killikelly | The assessment of grief in refugees and postconflict survivors: a narrative review of etic and emic research[END_REF], include one item regarding distressing preoccupation with the circumstances of the death. It also incorporates a Traumatic Bereavement Specifier (TBS), which is endorsed if the death occurred under violent or traumatic circumstances (i.e., homicide, suicide) or by generating distress in response to loss reminders (vivid thoughts, images, or feelings related to traumatic features of the death).

In accordance with the MGT, whether these clinical categories are conceptually distinct may relate to different causal precursors (e.g., sociodemographic risk factors, death-related circumstances), causal consequences (e.g., functional impairment or developmental progression), and primary mediators and moderators (e.g., trauma and loss reminders, secondary stressors and adversities, cultural norms) [START_REF] Kaplow | Using multidimensional grief theory to explore the effects of deployment, reintegration, and death on military youth and families[END_REF][START_REF] Kaplow | Persistent complex bereavement disorder as a call to action: using a proposed DSM-5 diagnosis to advance the field of childhood grief[END_REF]Layne et al., 2017a). Furthermore, to explain how posttraumatic stress symptoms can interfere with adaptive grieving and mourning, the MGT proposes a variety of potential mechanisms of interference. These include: (1) interference by reexperiencing posttraumatic stress symptoms through remembering and reminiscing, (2) cognitive and/or behavioral avoidance, (3) functional impairment that impedes efforts to carry on the legacy of the deceased, and (4) interference with the ability to find meaning in death. Likewise, many grief reaction mechanisms may interfere with recovery from posttraumatic stress reactions: (1) inability to accept the reality of the death, (2) avoidance of loss reminders interfere with confronting the reality of death, (3) survivor's guilt or stigma connected to the manner of death interferes with processing its traumatic circumstances, (4) existential crises precipitated by the loss may induce demoralization, nihilism, and motivation to recover, (5) intense sorrow, loneliness and withdrawal provoked by the loss, (6) stress evoked by secondary adversities (e.g., community and family disruption) and loss reminders (Layne et al., 2017a).

There is mounting evidence stemming from non-systematic reviews, although based on general community-based samples, that traumatic deaths heighten the risk for persistent post-bereavement distress, depression, and PTSD, often concomitantly [START_REF] Hibberd | Risk and protective factors for posttraumatic stress disorder, prolonged grief, and depression in survivors of the violent death of a loved one[END_REF][START_REF] Kristensen | Bereavement and mental health after sudden and violent losses: a review[END_REF]. Beyond the TBS related to PCBD, the MGT proposes considering the role played by the cause of death [START_REF] Kaplow | Using multidimensional grief theory to explore the effects of deployment, reintegration, and death on military youth and families[END_REF][START_REF] Kaplow | Persistent complex bereavement disorder as a call to action: using a proposed DSM-5 diagnosis to advance the field of childhood grief[END_REF]Layne et al., 2017a), which potentially contains traumatogenic elements capable of evoking circumstance-related grief reactions, PTSD, or both [START_REF] Kaplow | Persistent complex bereavement disorder as a call to action: using a proposed DSM-5 diagnosis to advance the field of childhood grief[END_REF]. These considerations warrant further examination, especially among bereaved refugee populations, given that pathological grief has recently gained consensus as a distinct clinical entity. Generally, death(s) can occur cumulatively with traumatic events in the homeland before or during forced displacement into the host country. A study by [START_REF] Claycomb | Persistent complex bereavement disorder symptom domains relate differentially to PTSD and depression: a study of war-exposed Bosnian adolescents[END_REF] showed that Bosnian adolescents who had experienced cumulative grief following the deaths of loved ones due to the Bosnian civil war and deaths not related to the war scored higher on PCBD, PTSD, and depression measures than a matched group who struggled solely with either war-related deaths or non-war-related deaths. Prior research has suggested that maladaptive grief reactions may interfere or overlap with PTSD [START_REF] Green | Traumatic loss: conceptual and empirical links between trauma and bereavement[END_REF]Nakajima et al., 2012;[START_REF] Neria | Bereavement by traumatic means: the complex synergy of trauma and grief[END_REF][START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF][START_REF] Regehr | Intersections between grief and trauma: toward an empirically based model for treating traumatic grief[END_REF]. According to some researchers (e.g., [START_REF] Armour | Violent death: understanding the context of traumatic and stigmatized grief[END_REF]Layne et al., 2017a), the complex interrelation of trauma reactions and grief may delay recovery.

Given that bereaved immigrants and refugees endure many deathrelated experiences, they constitute an ideal sample to explore relations between prolonged grief reactions, posttraumatic stress reactions, and other comorbidities. For our analyses, the term(s) "refugees" or "immigrants and refugees" refer to immigrants displaced outside their home countries (versus internally displaced persons) -disconnected from their cultural groups. This definition includes asylum seekers as defined in 1951 by the Geneva Convention relating to the status of refugees. We specifically focused on bereaved adult immigrants and refugees because PCBD and PGD clinical criteria were conceptually rooted in adult samples. Moreover, bereavement research on children and adolescents involves important developmental considerations that are not examined in this review. Thus, advancing the phenomenological understanding of this issue may contribute to elucidating the complex associations between bereavement and trauma. By doing so, future theory building studies may better explain the (causal) risk factors associated with grief-related disorder(s), as well as mechanisms that interfere with adaptive grieving following the death of a loved one [START_REF] Kaplow | Using multidimensional grief theory to explore the effects of deployment, reintegration, and death on military youth and families[END_REF][START_REF] Kaplow | Persistent complex bereavement disorder as a call to action: using a proposed DSM-5 diagnosis to advance the field of childhood grief[END_REF]Layne et al., 2017a). Bereaved immigrants and refugees also serve as ideal populations for understanding how cultural and religious norms shape certain aspects of PCBD symptom manifestation [START_REF] Smid | Toward cultural assessment of grief and grief-related psychopathology[END_REF]. Finally, we believe that in the face of armed conflicts, disasters, climate change, and millions of refugees being driven away from their homes worldwide, the topic of trauma and bereavement/grief merits increased clinical attention. Hence, refugees varied cultural backgrounds must be kept in mind when considering cultural variability in adjusting to trauma and loss, specifically among those with presumed trauma or grief-related disorders [START_REF] Eisenbruch | The cultural bereavement interview: a new clinical research approach for refugees[END_REF][START_REF] Eisenbruch | From post-traumatic stress disorder to cultural bereavement: diagnosis of southeast asian refugees[END_REF][START_REF] Rosenblatt | Grief: what we have learned from cross-cultural studies[END_REF][START_REF] Smid | Toward cultural assessment of grief and grief-related psychopathology[END_REF].

Globally, the present review attempted to clarify two major questions surrounding the nature, breadth, and main features of the current grief diagnosis construct (PCBD and PGD). The first question we addressed was: What are the estimated prevalence rates, comorbid conditions and features of the grief disorder (referred to as complicated grief, PCBD and PGD) among bereaved refugees? Accordingly, the purpose of this review was to estimate the pooled prevalence of grief disorders and to examine its consequences and primary correlates (including comorbidities). The secondary purpose sought to understand how grief disorder and PTSD symptoms intersect or interfere with each other. The second question was: Beyond variations in the definition and operationalization of grief disorder, what relevant causal risk factors and protective factors are associated with grief disorder and comorbidities? To answer this question, we reviewed diverse sociodemographic and bereavement-related risk factors and protective factors associated with grief disorder and mental health related outcomes.

Methods

Data sources and search strategy

Five electronic databases (PsycINFO, PsycARTICLES, Psychology and Behavioral Sciences Collection, Academic Search Elite, and PubMed) were systematically searched to identify potentially relevant articles. We used a combination of keywords with Boolean operators, all of which relied on narrower criteria ([grief OR bereav* OR mourn* OR loss OR widow*] OR [trauma*, posttraumatic stress] AND [asylum seeker or refugee or immigra* or migra*] AND [health OR well-being OR disorder OR quality of life OR distress* OR depress* OR anxiety OR somati*]). The terms trauma* and posttraumatic stress were included in our search syntax as we presumed that grief phenomena are often studied separately in trauma research. We also searched Google Scholar and explored reference lists manually to find additional suitable articles not identified by our search algorithm.

Inclusion and exclusion criteria

The eligibility criteria included quantitative studies published in peer-reviewed journals without language restrictions. The studies had to survey adult bereaved immigrants, refugees, or asylum seekers and addressed any type of death regarding a relationship to the deceased, whether the death occurred in the homeland, during displacement/ migration, or in the resettlement country. Included studies also had to use an assessment tool of grief symptoms or at least address co-occurrence/comorbid conditions such as PTSD, depression, and anxiety.

We excluded articles targeting internally displaced persons (IDP) because, as stated earlier, these individuals generally maintain direct bonds with their home country. The second reason related to homogeneity analysis; a meta-analysis by [START_REF] Porter | Predisplacement and postdisplacement factors associated with mental health of refugees and internally displaced persons: a meta-analysis[END_REF] reported a substantially lower magnitude of psychological distress among IDP than among refugees. Moreover, studies that focused on child and adolescent refugees were not included. Studies on grief non-related to death, such as cultural bereavement or migratory grief were also excluded, as were studies that pertained to ambiguous loss related to missing close persons, as the grieving process may not occur until the reality of the death becomes evident (e.g., Heeke, Stammel, & Knaevelsrud, 2015;[START_REF] Lenferink | Toward a better understanding of psychological symptoms in people confronted with the disappearance of a loved one: a systematic review[END_REF]. Studies on treatment outcomes or on intervention or prevention programs that included our target population were also excluded. Finally, case studies, theoretical reflections, opinion-based articles, and abstracts were excluded. The final search was run in August 2018.

Study selection and data extraction

The study selection process was designed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [START_REF] Moher | Preferred reporting items for systematic reviews and meta-analyses: the prisma statement[END_REF], see Fig. 1). Data were extracted from each included study as follows: a) basic information of a study: name of the first author, year of publication, sample size, study design, data collection methods; b) demographic characteristics: participants sex, mean age or range, participants country of origin, host country, mean length of stay; c) information about death and trauma: mean time passed since the death of a loved one, relationship to the deceased person, cause or specific context of the death (including traumatic events surrounding the death); d) outcome variables: grief reactions, post-traumatic stress reactions, anxiety, depression, somatic complaints; and e) relevant results in line with the purposes of this review.

Quality assessment

Two investigators (CKK and JMC) independently evaluated eligible papers. When discrepancies occurred, they adopted a consensus principle and if necessary, consulted a third reviewer (AB). Table 1 provides characteristics relating to the quality of the studies selected for the review, using the Newcastle-Ottawa Scale (NOS) [START_REF] Wells | The Newcastle-Ottawa scale(nos) for assessing the quality of nonrandomised studies in meta-analyses[END_REF]. Due to the cross-sectional design used by the studies reviewed, the NOS was somewhat modified. The total score of the NOS rating ranged from 0 to 12 and covered three domains: the selection and sampling (3 points), outcomes assessment (4 points), and results reporting (5 points). By following [START_REF] Landis | The measurement of observer agreement for categorical data[END_REF] recommendations (< 0.00 = poor; 0.00-0.20 = slight; 0.21-0.40 = fair; 0.41-0.60 = moderate; 0.61-0.80 = substantial; and 0.81-1.00 = almost perfect), we interpreted the kappa coefficient value for inter-rater agreement for coding study quality as substantial (k = 0.76; ES = 0.14).

Synthesis of results

First, an overview of the main characteristics of the studies reviewed is provided. Next, individual studies that reported the prevalence rate of PGD were stratified. Then, the pooled prevalence estimate with a 95% confidence interval (CI) of PGD was calculated using random effects meta-analysis of proportions through statistical software MedCalc Version 19.1 (2019). Heterogeneity was assessed using I 2 statistics, a measure of the proportion of variation [START_REF] Higgins | Measuring inconsistency in meta-analyses[END_REF]. A value of approximately 0 suggests homogeneity, whereas values of 25-50%, 50-75% and 75-100% represent low, medium and large heterogeneity, respectively [START_REF] Higgins | Measuring inconsistency in meta-analyses[END_REF]. Meta-analyses were also performed on correlates that were measured in at least two studies; Pearson's correlation coefficient r was used as a measure of effect size [START_REF] Borenstein | Introduction to Meta-Analysis[END_REF].

For the remaining analyses, the heterogeneous constituents (e.g., types of variables, small number of studies per variable and per outcome, missing data) led us to adopt a descriptive narrative synthesis [START_REF] Cooper | Synthesizing Research: a Guide for Literature Reviews[END_REF][START_REF] Whittemore | The integrative review: updated methodology[END_REF]. Therefore, the main results extracted from each study are categorized and summarized in light of the MGT premises, which framed the review objectives.

Results

Fig. 1 shows a PRISMA flow diagram of the article selection process. The initial search generated 126 potentially relevant papers. After removing duplicates, the search yielded 86 records. An additional 49 articles that did not satisfy the inclusion criteria at the abstract level were removed. When two or more papers used the same sample, we included those that presented relevant results to this review. Finally, 12 studies met the inclusion criteria.

Description of study characteristics

Table 2 provides the characteristics and main results of each study in detail. The included studies were published between 1998 and 2018, thus spanning two decades of research.

Country of origin and sample

Four studies were conducted in the U.S, three in Australia, two in Papua New Guinea and two in the Netherlands, one in France and Belgium, respectively. All studies investigated immigrant and refugee samples from non-Western developing countries. The total of all the samples combined was of 2439, with a mean size of 203.3 (range: 74 to 486). Females represented 51.5% of the overall sample and age ranged from 18 to 88. In five samples, participants had attended secondary school or higher education, more specifically college or university. In two samples, the mean number of years of education exceeded 10.

Bereavement-related characteristics

Across seven studies, the time span since bereavement(s) varied considerably in average, ranging from less than 12 months to 28.9 years. Most of the deaths studied occurred during the Cambodian Pol Pot Genocide, the Bosnian and Kosovo civil wars and focused on public murders or executions, acts of torture, persecutions, extra-judicial detention, starvation or diseases. Five studies reported multiple losses [START_REF] Caspi | Relationship of child loss to psychiatric and functional impairment in resettled Cambodian refugees[END_REF][START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF]Hinton et al., 2013aHinton et al., , 2013b;;[START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF]. Deaths of grandparents or family members were reported in five studies, deaths of friends, colleagues or parents in four studies, deaths of children and siblings in three studies, and deaths of spouses in one study.

Assessments

All studies used a cross-sectional design, two of which used a comparative cross-sectional design [START_REF] Caspi | Relationship of child loss to psychiatric and functional impairment in resettled Cambodian refugees[END_REF][START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF]. Ten studies assessed grief reactions by using different versions of grief construct measures, which induced inconsistencies in terminology: Inventory of Complicated Grief (ICG; Prigerson et al., 1995), Prolonged Grief-13 (PG-13;[START_REF] Prigerson | Prolonged grief disorder: psychometric validation of criteria proposed for DSM-V and ICD-11[END_REF], items derived from the DSM-5 PCBD and the ICD-11 PGD, and Core Bereavement Items (CBI; [START_REF] Burnett | Measuring core bereavement phenomena[END_REF]. Eleven studies assessed PTSD symptoms, 8 depression and suicide risk, 3 anxiety and 2 somatic syndromes and guiltrelated grief. Seven studies assessed causal consequences of grief, including functional impairment/disability, general health and quality of life.

0 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 1 1 1
Note: A1 was rated 2 when it was a random sampling and 1 when it was non-random sampling. B1 was rated 2 when the study used valided measures.

(continued on next page) Note: F= female; M= male; CSS = cross-sectional study; SD( ± )= standard deviation; NR = not reported; CG = complicated grief; PCBD = persistent complex bereavement disorder -cf. DSM-5; PGD = prolonged grief disorder -cf. forthcoming ICD-11; CBI = core bereavement items; GMH = general mental health; MDD = major depression disorder; MDE = major depression episode; PTSD = post-traumatic stress disorder; ADAPT = adaptation and Development after Persecution and Trauma.

Methodological quality of studies

The methodological quality of the included studies was assessed based on the NOS. The average quality of the included studies was of 9.47 (SD = 2.06, range: 5-12). Three studies scored above the 75th percentile and five, under the median. Five studies used random sampling techniques. Nine studies (75%) used face-to-face interviews and three (25%) used self-report questionnaires. Almost all studies employed reliable measures that underwent forward and back translation to the local language(s), and 50% reported sufficient psychometric properties of the measures used. In half of the studies, possible confounders such as time passed since bereavement, relationship to the deceased, cause of death, and length of stay in the resettlement country were not examined or controlled for in statistical approaches.

Estimated prevalence of prolonged grief disorder

Four studies were eligible for a meta-analysis on the prevalence of PGD [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF]Hinton et al., 2013b;[START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF][START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF]. The pooled prevalence estimate using a random effect model was of 33.2% (95% CI: 15.2-54.2%), with a high degree of inconsistency (I 2 = 95.48%, Q = 66.42, df = 3, p < 0.0001).

Causal consequences of prolonged grief disorder

PGD was negatively associated with well-being and general mental health [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF]. After controlling for demographics, PGD significantly predicted general mental distress, somatic complaints, grief-related functional impairment, severity of suicide risk over and above PTSD, and/or major depression episodes [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF]Hinton et al., 2013b;[START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF]. Using multilevel path analysis, Nickerson et al.'s (2011) study on Mandaean refugees, which grouped participants at both individual and family levels, supported the above-mentioned results; however, at the family level, PGD accounted for 64% of the variance in mental health variables, whereas PTSD accounted for 46% of the variance. In contrast, at the individual level, PGD scores predicted variance in mental health variables (R 2 = .19) less so than PTSD symptoms (R 2 = .33).

Primary correlates/comorbid conditions

Based on three studies [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF][START_REF] Momartin | Complicated grief in Bosnian refugees: associations with posttraumatic stress disorder and depression[END_REF][START_REF] Nickerson | The familial influence of loss and trauma on refugee mental health: a multilevel path analysis[END_REF], we found significant association between PGD and PTSD (r = 0.47, p = 0.041, 95% CI: 0.02-0.76) and between PGD and depression (r = 0.52, p < 0.01, 95% CI: 0.34-0.65), with large heterogeneity across studies (I 2 = 96.74%, Q = 61.41, df = 2, p < 0.0001, and I 2 = 82.7%, Q = 11.56, df = 2, p = 0.003, respectively). In one study, PGD was also associated with anxiety [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF]. Using latent class analysis (LCA) followed by multinomial logistic regressions, [START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF] found that disrupted interpersonal bonds and confusion about one's role and identity, respectively, were associated with PTSD/PGD. [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF] found that almost all PGD items (e.g., longing or yearning, difficulty accepting the death of a loved one, difficulty trusting others, difficulty moving on, bitterness, numbing, emptiness, feeling jumpy) were endorsed in PTSD/PGD, but not in PTSD and in PGD. Conversely, only PTSD-items related to intrusive memories were endorsed in PTSD/PGD, PTSD, and PGD, whereas PTSD-avoidance symptoms (avoidant thoughts and activities) and most PTSD-numbing symptoms (loss of interest, feeling detached, and having a sense of foreshortened future) were significant predictors of PTSD. In both studies [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF][START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF], PTSD affected approximately 10% of bereaved individuals. Using a regression analysis, Hinton et al. (2013b) found that 38% of the variance in PTSD severity was due to a single item on recalling pain regarding the deceased among Cambodian refugees. Recalling pain most frequently concerned the rebirth of the deceased parent and induced crying episodes lasting approximately 11 min in the last month accompanied by palpitations, tinnitus, and headaches (Hinton et al., 2013a). Additionally, functional impairment (59%) was a common severe bereavement-related symptom (Hinton et al., 2013a(Hinton et al., , 2013b)). Similarly, [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF] found that refugees scored higher on every ICG item and differed significantly from non-refugee immigrants in avoiding reminders of the deceased, functional impairment, but also in experiencing subsequent difficulty in accepting the death and emptiness.

Sociodemographic and causal risk factors

Sociodemographic risk factors

Gender. Pooling the estimates from 6 of 7 studies examining sexrelated risk factors for PGD [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF]Hinton et al., 2013b;[START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF][START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF][START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF][START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF], the results of the meta-analysis showed no significant association (r = 0.08, ns). However, females were at higher risk for PTSD/PGD [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF], PTSD, depressive and anxiety symptoms, general health distress and somatic complaints [START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF][START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF].

Age. Three out 6 studies found that older refugees were more likely to exhibit severe prolonged grief reactions [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF][START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF] or disability [START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF].

Education. Only one study revealed that immigrants and refugees who had attended university reported fewer grief symptoms [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF]. Nevertheless, higher education seemed to be a protective factor for PTSD, depression, and anxiety [START_REF] Craig | Complicated grief and its relationship to mental health and well-being among Bosnian refugees after resettlement in the United States: implications for practice, policy, and research[END_REF].

Other sociodemographics. A study by Kokou-Kpolou et al. ( 2017) found that immigrants and refugees who were the eldest siblings, married or in a common-law union, and unemployed were more at risk for increased PGD symptoms. Also, an immigration status associated with constraints regarding refugee status, and staying over 10 years in the host country were found to increase PGD severity [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF].

Bereavement and trauma risk factors 3.5.2.1. Relationship to the deceased.

In four studies that examined the impact of the relationship to the deceased, the death of first-degree relatives (parent, child) was found to have a moderate to high effect on PGD [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF] and comorbidities [START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF][START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF]. In contrast, [START_REF] Caspi | Relationship of child loss to psychiatric and functional impairment in resettled Cambodian refugees[END_REF] found no association between loss of a child and PTSD, depression, and anxiety, but they discovered a significant association with self-perceived health, cultural-dependent depressive state (e.g., "a deep worrying or sadness not visible to others"), and somatic symptoms (e.g., poor vision, bodily pain, numbness).

Traumatic and multiple deaths, and trauma events.

Four studies revealed that traumatic deaths (e.g., war-related death of one's father) predicted PGD [START_REF] Momartin | Complicated grief in Bosnian refugees: associations with posttraumatic stress disorder and depression[END_REF]Tay et al., 2015), PTSD/PGD [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF], and disability [START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF]. In a sample of Bosnian Muslim refugees, [START_REF] Momartin | Complicated grief in Bosnian refugees: associations with posttraumatic stress disorder and depression[END_REF] reported significant correlations that were moderate in strength between CBI related to distressing images and thoughts, traumatic losses, and human right violations, respectively. However, these correlations did not encompass "acute separation". Three studies reported significant associations between traumatic events (detention, abuse) and PGD [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF], PTSD/PGD [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF][START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF], and PTSD [START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF]. [START_REF] Morina | War and bereavement: consequences for mental and physical distress[END_REF] reported that bereaved refugees (youth) whose fathers were killed during the Kosovo war presented major depression episodes (MDE), combined MDE/PTSD, and combined MDE/anxiety. In addition, [START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF] found that both multiple deaths and exposure to traumatic events are risk factors which significantly explain PTSD, depression, anxiety, disability, and worse quality of life after adjusting for demographics and secondary stressors. Secondary stressors, mainly long asylum procedures and postmigration stressors emerged as consistent predictors of PTSD.

Indirect effects and moderators

Two studies highlighted the role played by secondary stressors and adversities in increasing post-traumatic stress and grief distress. By performing a pathway analysis, Tay et al. (2015) identified persisting worries about the family (e.g., about loss and separation from family, about the wellbeing of family members) among west Papuan refugees as exerting an indirect effect on the path from traumatic losses to PTSD. Persisting worries may result in family disruption and in medical illnesses among family members resettled in different communities and/ or left behind in their home country, which raised feelings of injustice among Tay et al.'s sample (2015). Likewise, [START_REF] Hengst | The effects of traumatic and multiple loss on psychopathology, disability, and quality of life in Iraqi asylum seekers in the Netherlands[END_REF] found that witnessing the death of family members exerted a significant effect on disability.

Moreover, without explicitly stating moderating roles, four studies addressed culturally specific factors that may affect grief processes among bereaved immigrants and refugees. Hinton et al. (2013aHinton et al. ( , 2013b) ) found that 70% of those suffering from painful memories of the deceased attributed these symptoms to khyâl attack (a cultural explanatory model of somatic symptoms), while those who were preoccupied by concerns that the deceased had not yet been reborn in the afterlife had painful and upsetting dreams about the deceased in the last month. They also highlighted that concerns about rebirth status were highly correlated with PGD severity. In Caspi et al.'s study (1998), bereaved Cambodian refugee parents who lost their children expressed an increased need for engagement in spiritual practices by frequently visiting the temple. [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF] found that 64.9% of bereaved immigrants and refugees performed cultural rituals related to death or mourning; this participation was associated with decreased grief reaction severity, but with a small effect. Some studies implicitly mentioned that some bereaved refugees were opposed to performing these rituals (Hinton et al., 2013a;Tay et al., 2015).

Discussion

Summary of the main findings

In this review, pooled prevalence, primary correlates, and risk factors of grief disorder(s) were investigated among bereaved adult refugees. Table 2 presents all the studies that have been included and discussed in this review, as well as their main findings. The pooled prevalence of PGD using a random effect model was estimated around 33.2% (95% CI: 15.2-54.2%). In line with prior research in non-refugee populations (e.g., [START_REF] Boelen | Symptoms of prolonged grief, depression, and adult separation anxiety: distinctiveness and correlates[END_REF][START_REF] Boelen | The influence of symptoms of prolonged grief disorder, depression, and anxiety on quality of life among bereaved adults[END_REF], PGD cooccurred with PTSD, depression, and anxiety. PGD and PTSD/PGD intersected with PTSD-intrusions and painful memories. Although they overlapped, PGD independently predicted greater variance of health and functional impairments, demonstrating the incremental validity of PGD. The most consistent risk factors associated with PGD and PTSD/ PGD were being an older refugee and experiencing trauma and multiple deaths involving first-degree relatives. Although requiring further research for confirmation, witnessing the death of family members and persistent worries about loss and separation from family were found to play an indirect effect on traumatic losses, PTSD and disability, respectively. Similarly, taking into account the limited number of studies, the role of sociodemographic variables such as education, sibling order, employment, marital status, immigration status and the length of residence in the host country require further examination.

General interpretation of the review findings

Prevalence, comorbidities and consequences of PGD

The pooled prevalence of PGD among bereaved refugees was extremely high. It fell within a range of 14 -76% among traumatized bereaved individuals following the death of a loved caused by a disaster [START_REF] Kristensen | Bereavement and mental health after sudden and violent losses: a review[END_REF]. This demonstrates the psychopathological impact of traumatic and multiple death(s) of close relatives which are experienced by adult immigrants and refugees. Indeed, traumatic and multiple deaths trigger complex patterns of psychological states and feelings, encompassing prolonged grief reactions, and post-traumatic stress reactions, among others. The intersection between these common psychiatric disorders is unsurprising, as these results consistently align with existing bereavement literature (e.g., [START_REF] Boelen | Symptoms of prolonged grief, depression, and adult separation anxiety: distinctiveness and correlates[END_REF][START_REF] Boelen | The influence of symptoms of prolonged grief disorder, depression, and anxiety on quality of life among bereaved adults[END_REF]. However, they provide compelling evidence among traumatized bereaved refugees that the PGD construct is distinct from the PTSD one, thus corroborating previous research that has demonstrated the independent contribution of PGD to impaired functioning beyond PTSD and depression [START_REF] Boelen | Complicated grief, depression, and anxiety as distinct postloss syndromes: a confirmatory factor analysis study[END_REF]Bonanno et al., 2007;Suij et al., 2012). Hence, the results underscore the pressing need to pay special clinical attention to bereaved refugees confronting cumulative bereavement(s) and traumatic events, as they are more at risk for health and functional impairments.

The current review's findings also shed light on PGD symptoms and comorbid psychosomatic complaints among bereaved refugees. Factors included persistently high levels of somatic symptoms including blurry vision, dizziness, bodily pain, palpitations, numbness, and tinnitus. Reporting such psychosomatic manifestations in non-Western immigrants and refugees is consistent with the abundant literature on cultural variations in expressions of distress, as well as ethnocultural and symbolic systems to that attribute different meanings to distress [START_REF] Kirmayer | Culture and somatization: clinical, epidemiological, and ethnographic perspectives[END_REF][START_REF] Kokou-Kpolou | Étude des liens entre deuil, dépression et troubles somatiques auprès d'une population d'immigrés ouest-africains en Europe [Association between mourning, depression and somatic symptoms. results from a sample of west African immigrants in Europe][END_REF]. However, one could argue, by considering recent empirical research, that these culture-bound syndromes may not be exclusively rooted in cultural systems [START_REF] Afari | Psychological trauma and functional somatic syndromes: a systematic review and meta-analysis[END_REF]Escobar & Gureje, 2007). For example, with respect to the recent meta-analysis on a multiethnic sample by [START_REF] Afari | Psychological trauma and functional somatic syndromes: a systematic review and meta-analysis[END_REF], war exposure was the single best predictor of functional somatic syndromes.

Interrelation between PTSD and PGD

There are some compelling findings among studies that used LCA [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF][START_REF] Tay | Defining a combined constellation of complicated bereavement and PTSD and the psychosocial correlates associated with the pattern amongst refugees from West Papua[END_REF]; they consistently yielded combined PTSD/PGD, which was endorsed by nearly 11% of bereaved refugees. PTSD/PGD captured specific items that encompassed certain DSM-5 PCBD items, such as disrupted interpersonal bonds and networks, and confusion about one's role and identity (disruptions in personal and social identity). In accordance with the MGT, such items evoke existential and identity distress and challenge the effort to find sense to the loss and a renewed sense in one's personal life following the death (Layne et al., 2017a). These results provide further information on PCBD criteria, specifically in relation to separation distress and circumstance-related distress (e.g., preoccupation with the circumstances of the death, preoccupation with the deceased person). As shown in Hinton et al. (2013aHinton et al. ( , 2013b) ) studies, intrusive memories expressed through recalling pain were impacted by the traumatic circumstances of the death and by rebirth concerns of the deceased. This aligns with the MGT premises in that circumstance-related distress evokes troubling thoughts and fantasies by focusing on the way the person died (Layne et al., 2017a). Hence, it is of importance to devote a particular attention to the TBS among bereaved refugee populations, as proposed by the DSM-5 when investigating grief-related disorder(s). This seems relevant for differential diagnosis, as the DSM-5 PTSD diagnosis now includes a statement indicating that traumatic experiences involving violent death(s) may result in a significant interaction between problematic bereavement reactions and PTSD (APA, 2013;Layne et al., 2017a). In sum, the DSM-5′s PCBD construct appeared to be an advantageously appropriate diagnostic construct for traumatically bereaved populations.

Furthermore, in both studies that used LCA, only one PTSD item on intrusive memories was associated with PGD, PTSD/PGD, and PTSD. In other terms, trauma and bereavement intersect with intrusive memories. This result empirically supports the first theorized mechanism that PTSD and PCBD interfere with each other (Layne et al., 2017a). Traumatized, bereaved adult refugees may thus be prone to re-experiencing past trauma events through pained memories of the deceased. The results also showed that most PTSD symptoms (e.g., psychological or physiological distress due to reminders, startle reactions, irritability, insomnia, difficulty concentrating) overlay with combined PTSD/PGD symptoms, but not with PGD [START_REF] Nickerson | Posttraumatic stress disorder and prolonged grief in refugees exposed to trauma and loss[END_REF]. Although responses to trauma differ from responses to bereavement in several respects, these findings suggest that for traumatized and bereaved refugees, the memories of their lost loved one(s) tend to become inextricably linked to the memories of the violent causes of the death. They also shed light on preliminary work by [START_REF] Pynoos | Grief and trauma in children & adolescents[END_REF] see also Layne et al., 2017b) which revealed that bereaved children and youths with posttraumatic stress reactions could focus their mental efforts on the traumatic circumstances surrounding the death, thus inhibiting their capacity to grieve adaptively and adjust to the loss.

Indirect effects of trauma and loss reminders

As conceptualized by the MGT, trauma and loss reminders, as well as secondary stressors play a prominent role as mediators between the death of close relatives which occurred under traumatic circumstances and the adjustment period following the bereavement [START_REF] Layne | Contextual influences on post-traumatic adjustment: retraumatization and the roles of distressing reminders, secondary adversities, and revictimization[END_REF](Layne et al., , 2017a)). This assumption is corroborated by two preliminary findings which emerged from this review. Witnessing the violent death of family members (e.g., public execution) and persistent worries about loss and separation from family were found to exert an indirect effect on the path from traumatic losses to PTSD and disability, respectively. Until further confirmation is provided, these variables may trigger remembering the circumstances surrounding the death(s), which may then prolong distress and increase the risk of disability or functional impairment.

Risk factors for PGD and comorbidities

Bereavement-related risk factors

The most robust etiologic risk factors found in the present review were multiple and traumatic deaths direct predictive effect on PGD, PTSD/PGD, depression, and disability, which were examined by seven studies and demonstrated by six of them. These findings confirm results from prior non-systematic reviews using general community-based samples that violent deaths following disasters increase the risk for persistent post-bereavement distress, PTSD, and depression, often concomitantly [START_REF] Hibberd | Risk and protective factors for posttraumatic stress disorder, prolonged grief, and depression in survivors of the violent death of a loved one[END_REF][START_REF] Kristensen | Bereavement and mental health after sudden and violent losses: a review[END_REF]. They also corroborate those of Claycomb et al.'s (2016), which indicate that youth accumulating losses and exposed to both war-related deaths and deaths unrelated to war scored higher on PCBD, PTSD, and depression measures than youth solely bereaved by deaths due to war. Indeed, multiple and cumulative deaths leading to a ʻbereavement overload', as called by [START_REF] Neimeyer | Bereavement overload[END_REF], is thought to generate a cascade of intrusive distressing mental images associated with many trauma and loss reminders, which undermines the ability to cope adequately [START_REF] Layne | Contextual influences on post-traumatic adjustment: retraumatization and the roles of distressing reminders, secondary adversities, and revictimization[END_REF]. We found that study samples that examined multiple and traumatic losses all included the death of at least one family member. Thus, the nature of the relationship to the deceased person and the brutality of the death may cause a destructive break, disabling the capacities to symbolize and recall the loss. Hinton et al. (2013b) showed that refugees not only suffer from complex traumatic bereavement(s) but also from the impossibility of performing prescribed mourning rituals. It is well known that in war contexts, families are often unable to bury their relatives in a dignified manner, sometimes without the body or with mutilated bodies. Enduring such a horrific traumatic death may lead to retaliatory fantasies and cognitive distortions that impede the grieving process. Hence, performing "substitute" symbolic mourning rituals, as found by [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF] study, could alleviate grief reactions.

Sociodemographic risk factors

In this review, we found that females might be more at risk for comorbid PTSD/PGD, but not for PGD, implying that the increased vulnerability for females may depend on traumatic events surrounding the bereavement [START_REF] Hsu | Sex differences in intrusive memories following trauma[END_REF]. The data also suggested that older refugees were more likely to exhibit elevated grief reactions. Although these data are insufficient to provide evidence on the role of age, it seems that older refugees have experienced multiple traumas, including traumatic deaths and losses, which might undermine their resilience responses. Previous research has often reported that older refugees have greater difficulty adapting to their new social environment, which constitutes an additional source of stress.

Regarding other demographic variables such as education level and employment status, numerous studies have demonstrated their impacts on mental health among refugees (see Hynie, 2017 for review). These variables partially depend on integration policies for refugees in the resettlement countries. Occasionally, refugees are unemployed for many years and the longer they remain in the host country, the more economically impoverished and socially disintegrated they become. According to the MGT, involuntary unemployment, financial hardship, among other possible causes, are sources of secondary stress which complicate efforts to adjust to the loss and exacerbate existential and personal distress. With regard to the length of residence in the host country, in particular, [START_REF] Gimeno-Feliu | Multimorbidity and immigrant status: associations with area of origin and length of residence in host country[END_REF] demonstrated that risk of multimorbidity is two times higher among foreign-born immigrants residing in Spain for five years or more than among those residing in Spain for less than five years. [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF] also noted an eldest sibling position as a prominent risk factor for severe grief and feelings of guilt. Eldest sons were particularly affected by bereavement due to the weight of their hierarchy and the enormous expectations placed on them to bury their parent in a dignified manner and to manage parental inheritance. However, information about all selected sociodemographic factors was less consistent and requires further exploration.

Future research recommendations

The quality of the reviewed studies (see Table 1) and review findings demonstrate that empirical research in this field is in its early stages. Therefore, this review lays the foundation to improve further empirical research on bereavement and on grief among refugee populations. Building on the reported findings, we discussed the limitations of the current literature and provided concrete recommendations (see the lines below) that will rigorously advance the field.

• Reporting psychometric properties of measures used. In the studies re- viewed, we found that although great efforts were undertaken in translating measures, four did not provide enough psychometric properties for grief assessment tools and half of the studies did not do so for other outcome measures. We encourage all researchers to systematically report psychometric characteristics (e.g., internal reliability, sampling adequacy) of the measures used so that the readers may assess their psychometric accuracy in relation to non-Western bereaved refugee populations. To provide much-needed momentum to this field, we also encourage the transcultural validation of these measures among these populations.

• Methodological alignment with DSM-5-PCBD and ICD-11-PGD criteria. We also found the assessment of PGD to be methodically heterogeneous across studies with different cutoff criteria. Future research should prioritize a methodological alignment through the use of either the DSM-5-PCBD or ICD-11-PGD assessment tools, or both in a complementary approach (e.g., Traumatic Grief Inventory-Self Report, [START_REF] Boelen | Disturbed grief: prolonged grief disorder and persistent complex bereavement disorder[END_REF]Boelen et al., , 2019)). This could help with avoiding inconsistencies in terminology. For more detailed methodological issues, refer to the following review conducted by [START_REF] Killikelly | The assessment of grief in refugees and postconflict survivors: a narrative review of etic and emic research[END_REF], which extensively focuses on the assessment of grief among refugees and post-conflict survivors.

• Multi-informant assessment of primary correlates. Given the extremely complex nature of traumatic bereavement symptoms, we encourage using multi-informant assessment, including measures on grief (PCBD or ICD-11-PGD), PTSD, complex PTSD, peri/traumatic dissociation, depression, anxiety, etc. By using appropriate statistical methods, researchers could contribute to delineate the nature, extent, and content validity of the current grief diagnostic constructs (PCBD and PGD).

• Extending the TBS. The complexity of grief disorder patterns due to the violent deaths of loved ones and traumatogenic elements should be considered further in future studies. In light of our results, TBS should be extended beyond homicide and suicide deaths. It should also include war deaths, genocide deaths, disaster-related deaths, among others, and the traumatic circumstances surrounding the death(s) (e.g., torture, public execution, agony) when grief-related disorder(s) are investigated. To address this, we suggest to include a set of specific items that could capture the span of circumstancerelated distress precipitated by TBS. These items should be defined according to the PCBD criteria.

• Unpacking traumatic bereavement factors. Future research should systematically report and analyze all possible factors such as the time since the loss, the relationship to the deceased, the cause of the death(s) and other traumatic events surrounding the death(s). Attention should also be drawn to the length of residence in the host country as a key indicator in evaluating the course of grief reactions over time simultaneously with the adjustment to the host country environment; some studies have found a linear relationship [START_REF] Kokou-Kpolou | A cross-cultural approach to complicated grief reactions among togo-western African immigrants in Europe[END_REF] and curvilinear [START_REF] Tran | Nonlinear relationship between length of residence and depression in a community-based sample of Vietnamese Americans[END_REF] associations between this variable and psychological distress among refugee population. Furthermore, as proposed by the MGT (Layne et al., 2017a) and in line with preliminary evidence by Tay et al.'s (2015) study, additional research is needed to explore whether trauma reminders and loss reminders mediate the links between traumatic bereavement(s) and ongoing adjustment among refugees.

• Exploring culture-related grief beliefs and their meanings. The format of Western mental health assessments, as outlined above, could be paired with measures relying on ʻemic' concepts of distress or idioms of distress. For example, innovative tools such as the "Cultural Assessment of Grief and Grief-Related Psychopathology" proposed by [START_REF] Smid | Toward cultural assessment of grief and grief-related psychopathology[END_REF], could help to explore the cultural meaning behind the bereavement(s) refugees faced through semi-structured interviews. According to the MGT, cultural appraisal and meaning should be approached as moderators and mediators in the relationship between traumatic bereavement(s) and psychological adjustment to the loss.

• Focus on internal and external resources. The second purpose of this review was to identify the protective and adaptative factors among bereaved refugee populations. However, it is striking to note that almost all the studies did not emphasize these factors. Future studies would benefit the field by investigating variables that may predict better mental health and well-being. As reviewed by some authors [START_REF] Chan | Well-being after trauma: a review of posttraumatic growth among refugees[END_REF][START_REF] Siriwardhana | A systematic review of resilience and mental health outcomes of conflict-driven adult forced migrants[END_REF], family and community support, feelings of belonging to the same community, supportive relationships, and religious beliefs may enhance personal resilience capacities and coping responses when enduring adverse life events. This prompts a call to direct our efforts in investigating the internal and external resources that protect refugees against the disruptive impact of traumatic and multiple deaths and help them to grieve adaptively.

Conclusion

This review included 12 cross-sectional studies yielding moderate quality criteria. This time-sensitive study has pinpointed causal consequences, primary correlates and risk factors for grief-related disorders among immigrants and refugees who have lost significant others. While empirical research on this topic is in its early stages, this review has demonstrated that PGD, combined PGD and PTSD, depression, and disability form complex psychopathological comorbidities. The DSM-5′s PCBD seems to be a potentially good grief construct that accurately captures the broad spectrum of reactions manifested. These comorbidities are impacted by circumstance-related distress in the context of death(s), jointly influenced by ethnocultural belief systems expressed through somatization and idioms of distress, hence the importance of developing intercultural skills in managing such disorders. While demographic factors were mixed, thus needing further investigation, there was a robust trend of traumatic and multiple deaths predicting PGD and worse mental health outcomes. Due to upsurges in migratory fluxes, with conflict driving millions of refugees away from their homes worldwide, this topic will likely draw increasing clinical attention. In this respect, the present literature review has laid solid foundations for future empirical research in this ongoing scholarly field.

Fig. 1 .

 1 Fig. 1. PRISMA flow diagram for the selection process of included studies.

Table 1

 1 Quality appraisal of the 12 included studies.

	Criteria	Caspi et al.	Craig et al.	Hengst et al.	Hinton et al.	Hinton et al.	Kokou-	Momartin et al.	Morina et al.	Nickerson et al.	Nickerson et al.	Tay et al.	Tay et al.
		(1998)	(2008)	(2018)	(2013a)	(2013b)	Kpolou et al.	(2004)	(2011)	(2011)	(2014)	(2016)	(2018)
							(2017)
	A. Selection and sampling
	A.1. Truly (random sampling) 2	2	2	1	1	0	1	1	1	1	2	2
	or somewhat (non-
	random sampling)
	representative of the
	average in the target
	population
	A.2. The sampling method is	1	1	1	0	1	1	1	1	1	1	1	1
	described -Inclusion and
	exclusion criteria are
	stated
	B. Outcomes assessment
	B.1. Valid instruments used	2	2	2	-	2	2	2	2	2	2	2	2
	B.2. Psychometric proprieties
	are provided and
	sufficient
	B.3. Outcome assessment is
	multi-informant
	C. Results reporting
	C.1. Adequate characteristics
	of study participants (e.g.,
	demographic, clinical,
	social) are reported
	C.2. Adequate statistical
	analyses for addressing
	hypotheses
	C.3.The statistical test used is
	clearly described,
	including confidence
	intervals and the
	probability level (p
	value).
	C.4. Number of individuals at
	each stage of the study are
	provided; number of
	participants with missing
	data are reported for each
	variable of interest
	C.5. Possible confounders are
	examined and taken into
	account in the reporting
	of results

Table 2

 2 Description of the 12 included studies characteristics.

	Authors	Participants' country Host country;	Sample size Study	Participants' sex Mean age	Relationsh-Context, manner or type of	Mean time	Outcomes	Summary of main findings
	(Years)	of origin	Mean length of	(n)	design		( ± SD) or range	ip to	death (1) and Traumatic	since loss	variables
			stay		and data		(years)	deceased	events exposure (2)
					collection			person
	Caspi et al.-	Cambodia	USA	161	Compara-63.4%F, 36.6%	46.39	Child	Not all deaths, but some	NR	PTSD,	○ No association between loss of
	(1998)		(Massachusetts) 7		tive CSS,	M		(43.5%, up during Khmer Rouge.		depression,	child and psychiatric symptoms
			years		Random			to 6	Starvation, murder, disease,		anxiety,	(PTSD, depression, anxiety).
					Sample,			children)	death at birth (1) NR (2)		general health,	○ Significant group differences
					Face-to-						self-perceived	regarding self-perceived health,
					face						health, somatic	culture-dependent depressive state,
					interview						and emotional	somatic symptoms (poor vision,
											symptoms	bodily pain, numbness, poor
											(culture-	appetite).
											dependent	○ Relatively small differences
											depressive	between both groups in the
											state),	performance of actual daily and
											functioning	social activities.
											and functional	○ Parents whose children died were
											impairment	somewhat more inclined to visit the
												temple.
	Craig et al.-	Bosnia	U.S.	126	CSS,	56% F, 44% M	42	NR	Deaths during Bosnian civil	NR	PTSD, CG,	○ 54% met diagnostic criteria of
	(2008)		9 (6-12) years		Random				war (1)		anxiety,	CG.
					sample,				Been threatened to be killed		depression, and	○ Significant differences in level of CG
					Self-				by stranger, experiencing a		GMH	symptoms according to gender and
					reported				natural disaster, living in war			age.
					question-				zone (2)			○ CG positively associated to PTSD,
					naire							depression and anxiety, negatively
												associated with well-being and
												GMH.
												○ By adjusting for gender, age, and
												race, CG added to the prediction of
												GMH whereas addition of PTSD
												symptoms to the equation did
												reliably improve R2.
	Hengst et al.-	Iraq	Netherlands	294	CSS	35.4%F, 64.6%	35.4 ± 12.8	Family	Deaths caused by violence and	NR	PTSD, MDD,	○ Traumatic losses directly affect
	(2018)		20 months		Nonrand-	M		member	combat, unnatural deaths (1)		anxiety,	disability.
					om			(87.6%),	Lack of nutrition, experiencing		Quality of life,	○ After controlling for demographics,
					sample			friend	a natural disaster, exhausting		disabilities	traumatic events and secondary
					Face-to-			(49.5%),	during the flight (2)			stress (e.g., long asylum procedure,
					face			child				postmigration stressors), traumatic
					interview			(8.1%)				events and multiple losses have
												significant effects on all outcome
												variables.
												○ Unnatural and unexpected loss of
												child seemed to be the highest
												predictor of all outcomes variables.
												○ Female sex independently increased
												the risk for developing PTSD, MDD,
												and anxiety.
	Hinton et al. Cambodia	USA	100	CSS	65% F, 35% M	54.2 ± 7.5	Mean of	69% of the index losses	28.9 ± 11.-Bereavement	○ 76% had pained recall of a
	(2013a)		(Massachusetts)		Nonrand-			1.7 parents occurred during the Pol Pot	9	Questionnaire,	deceased person; the person most
			NR		om			( ± 0.5),	Genocide: starvation,		Somatic	frequently recalled in the last
					sample			2.1 siblings execution, illness (1)		symptoms	month (M = 5.1) was a parent,
					Face-to-			( ± 1.9),	NR (2)		(e.g., DSM-IV	followed by sibling, child.
								0.8			panic attack

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Table 2

 2 (continued)

	177

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Table 2

 2 (continued)

	178

Table 2

 2

		Summary of main findings			anger/negative appraisal; and	estrangement from others/social	impairment	○ No association between PGD and	sociodemographic factors (age,	gender, employment status,	marital status).	○ Disrupted interpersonal bonds and	networks was the only significant	predictor for complicated	bereavement.	○ Traumatic loss events, disrupted	interpersonal bonds and networks,	and disruption in roles and	identities predicted combined	posttraumatic bereavement (PGD/	PTSD).
		Outcomes	variables					Complicated	bereavement,	PTSD	symptoms,	postmigration	living	difficulties,	ADAPT
		Mean time	since loss					≤ 12	months
		of
		Context, manner or type	death (1) and Traumatic	events exposure (2)
		Relationsh-	ip to	deceased	person			Family	member	and/or	loved	(23.7%) -	one or	more loss	(es)
		Participants' sex Mean age	( ± SD) or range	(years)				44.1% F, 55.9% 35.8 ± 0.65	M
		Study	design	and data	collection			CSS-	Nonrand-	om	sample	Face-to-	face	interview
		Sample size	(n)					486
		Host country;	Mean length of	stay				Papua New	Guinea	15.6 ± 0.48 (for	43.1%)
	(continued)	Authors Participants' country	(Years) of origin					Tay et al.-West Papua	(2018)

Acknowledgements

We gratefully acknowledge the assistance of Hélène ELEOUET, research librarian at Picardy Jules Verne University, for her valuable support in articles search strategy. We would like to pay a posthumous tribute to our colleague, Dr. Daniel Mbassa Menick, who left us before the publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Contributions

Drs C.K.K., and C.S.M. conceived the original idea of this review. Dr. C.K.K. designed the study, wrote the manuscript. Drs C.K.K., and J.M.C. independently evaluated the eligible papers. Pr A.B. was the third reviewer. Drs C.S.M. and J.M. provided the advices on discussing the results, contributed to critically revising and proof-reading of the manuscript. Dr. J.M.C. provided critical feedback and helped shape the research. Pr MF.B. supervised the project, provided many suggestions to and approved the final manuscript.

Declaration of Competing Interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.