A meta-analysis of the association between posttraumatic stress disorder and suicidality: the role of comorbid depression
Introduction
Increased frequency of suicidal behaviors (suicidal thoughts, suicidal plans, or suicidal acts) has been reported in posttraumatic stress disorder (PTSD) [1], [2], [3], [4]. Similar to other common Axis I psychiatric disorders, such as major depression, substance use disorders, and psychoses, PTSD is strongly associated with increased frequency of suicidality [5], [6], [7], [8], [9], [10]. Comorbid psychiatric disorders and especially comorbid major depression have been found to substantially increase the levels of suicidality in those with PTSD [4], [11], [12], [13]. There is also some evidence that comorbid major depression mediates the relationship between suicidal ideation and PTSD [14]. One comprehensive narrative review has been published in the area of PTSD and suicidality, which aimed to summarize the available research findings on the relationship between suicidality and PTSD. Most of the studies indicated a strong positive association between PTSD and suicidality. The association between suicidality and PTSD appeared to hold across different populations, such as war veterans, victims of interpersonal victimization in childhood and/or in adulthood, PTSD samples with mixed traumas, psychiatric populations, and nonpsychiatric community samples. A considerable proportion of the studies also indicated that apart from PTSD, a diagnosis of major depression significantly increased suicidal risk. Moreover, the presence of PTSD and major depression comorbidity was associated with substantially increased suicidal risk compared with a PTSD diagnosis alone [15]. One important limitation of the above narrative review is that it was largely descriptive.
Meta-analytic procedures offer the best means of summarizing and statistically estimating the overall significance of findings derived from individual studies. One existing systematic review in the area of PTSD and suicidality indicated that a diagnosis of PTSD is positively associated with increased suicide attempts, and suicidal ideation, but not completed suicides. These findings were based on extracting and computing φ coefficients from 25 independent studies. This is a limited number of studies considering that more than 60 published studies have reported an association between PTSD and suicidality. In addition, no subgroup analyses were conducted to examine further the association of PTSD and suicidality. Finally, the authors concluded that the association between PTSD and suicidality remained after controlling for comorbid disorders including depression but also reported evidence that depression mediates the relationship between PTSD and suicidality [16]. Both of these contradictory outcomes concerning the role of depression in the association between suicidality and PTSD were based on a narrative interpretation of the extant literature and not by applying meta-analytic procedures.
Therefore, we conducted a comprehensive meta-analysis that aimed to expand and update the findings in the literature concerning the association between suicidality and PTSD. The term suicidality in this meta-analysis comprised a range of suicidal tendencies including suicidal thoughts, behaviors, plans, attempts, and successful suicides. The broad definition of suicidality used in this meta-analysis is justified by the following 2 reasons. First, the aim of this meta-analysis was to adopt an inclusive approach to provide a comprehensive quantitative account of the extant literature findings on PTSD and suicidality. After the results of the initial analysis of the link between suicidality and PTSD, a series of subsequent analyses (eg, subgroup analyses and meta-regression analyses) were planned to examine potential sources of heterogeneity among the studies included in the meta-analysis. Second, 2 previous reviews (1 narrative review and 1 systematic but less comprehensive review) in the area of PTSD and suicidality have been conducted, both of which used an equivalent definition of the term suicidality [15], [16]. The adoption of the same methodology with previous reviews in defining suicidality facilitates the direct comparison of the current findings with the results of these 2 reviews. The specific objectives of this meta-analysis were to (1) systematically quantify the research findings on the association of PTSD and suicidality across a large number of studies, (2) examine the association of suicidality and PTSD across different PTSD populations (ie, index trauma, psychiatric vs community samples) and across studies using different measures of PTSD (current vs lifetime, interviews vs questionnaires), and (3) examine the role of comorbid depression in the association between PTSD and suicidality by applying meta-regression procedures. Based on the existing literature, it was predicted that PTSD would be significantly positively associated with increased levels of suicide attempts and suicidal ideation. It was also predicted that the association between suicidality and PTSD would pertain across psychiatric and nonpsychiatric samples and across different trauma populations. Finally, it was hypothesized that the presence of comorbid depression would increase suicide risk in those with PTSD.
Section snippets
Inclusion and exclusion criteria
Studies were included in the meta-analysis if they met the following criteria:
- (a)
They were published in a peer-reviewed journal in the English language.
- (b)
They reported original research findings regarding the relationship between PTSD and suicidality.
- (c)
The sample comprised participants 15 years or older.
- (d)
They included any measure of PTSD and any measure of suicidality (suicidal ideation, plans, behaviors, attempts, and successful suicides).
- (e)
They contained outcome measures that reflected the association
Results
The search strategy yielded 246 results. Of these, 165 studies were empirical English-language studies. Of the 165 studies, 85 were identified as meeting the initial inclusion criteria. However, of the 85 studies, 19 did not provide an outcome measure of the association between PTSD and suicidality, and thus, they were excluded from further analysis. Two studies [1], [20] were excluded because they reported the same data in more recent articles [21], [22]. Finally, 5 studies assessed the
Discussion
The aim of the current meta-analysis was 2-fold: first, to examine the association between PTSD and suicidality and, second, to investigate the impact of depression on the association between PTSD and suicidality. Overall, the findings fully supported our initial hypothesis that a PTSD diagnosis would be associated with heightened rates of suicidality. In addition, consistent with our prediction, higher levels of comorbid depression in the PTSD groups compared with controls were associated with
Conclusions and implications
Taken as a whole, this pattern of findings confirms that PTSD, either as a primary or secondary diagnosis, is significantly associated with an increased risk for suicide. In addition, the findings of this meta-analysis further contribute to the existing literature, which indicates that individuals having psychiatric disorders are at increased risk for suicide [5]. Similarly to PTSD, a considerable number of other psychiatric diagnoses have been identified in the literature to compound risk for
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