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Abstract

Background

Traumatic events are common globally; however, comprehensive population-based cross-national data on the epidemiology of posttraumatic stress disorder (PTSD), the paradigmatic trauma-related mental disorder, are lacking.

Methods

Data were analyzed from 26 population surveys in the World Health Organization World Mental Health Surveys. A total of 71 083 respondents ages 18+ participated. The Composite International Diagnostic Interview assessed exposure to traumatic events as well as 30-day, 12-month, and lifetime PTSD. Respondents were also assessed for treatment in the 12 months preceding the survey. Age of onset distributions were examined by country income level. Associations of PTSD were examined with country income, world region, and respondent demographics.

Results

The cross-national lifetime prevalence of PTSD was 3.9% in the total sample and 5.6% among the trauma exposed. Half of respondents with PTSD reported persistent symptoms. Treatment seeking in high-income countries (53.5%) was roughly double that in low-lower middle income (22.8%) and upper-middle income (28.7%) countries. Social disadvantage, including younger age, female sex, being unmarried, being less educated, having lower household income, and being unemployed, was associated with increased risk of lifetime PTSD among the trauma exposed.

Conclusions

PTSD is prevalent cross-nationally, with half of all global cases being persistent. Only half of those with severe PTSD report receiving any treatment and only a minority receive specialty mental health care. Striking disparities in PTSD treatment exist by country income level. Increasing access to effective treatment, especially in low- and middle-income countries, remains critical for reducing the population burden of PTSD.

Introduction

Trauma is common globally. In a comprehensive report based on the World Mental Health (WMH) Surveys, Benjet et al. (2016) found that 70% of the populations in the countries studied reported exposure to a traumatic event, with exposure ranging from 29% in Romania to 83% in Peru. Although the majority of trauma-exposed individuals respond with resilience, a substantial minority go on to develop posttraumatic stress disorder (PTSD), the cardinal trauma-related mental disorder. PTSD often leads to very serious interpersonal and occupational challenges, and has been estimated to result in 3.6 days of lost productivity per month (Kessler, 2000). The disorder has been called a ‘life sentence’ due to its association with increased risk of chronic disease, accelerated aging, and premature mortality (Boscarino, 2006; Kubzansky et al. 2007; Miller & Sadeh, 2014; Roberts et al. 2015).

Previous studies have shown that the lifetime prevalence of PTSD varies widely across countries (Breslau, 2009). Surveys that ask about the worst event (identified by respondents) generally find higher rates of PTSD, ranging from 1.7% in South Korea (Jeon et al. 2007) to 9.2% in Canada (Van Ameringen et al. 2008), than surveys that assess PTSD in relation to an unspecified or random event, e.g. 2.3% in South Africa (Atwoli et al. 2013), 2.5% in Iraq (Alhasnawi et al. 2009), and 3.4% in Lebanon (Karam et al. 2008). The fact that prevalence estimates appear to vary widely by country suggests that an accurate picture of the worldwide prevalence of PTSD requires surveying countries across the global using a consistent instrument, sampling procedures, and analytic approach.

No previous report has brought together lifetime, 12-month, and 30-day PTSD prevalence across the full range of countries available in the WMH Survey. Lifetime prevalences provide an estimate of the proportion of the population that develops PTSD. Current or 12-month prevalences include both new (incident) and persistent cases. The proportion of 12-month cases among lifetime cases is informative as an indicator of persistent PTSD. However, 30-day prevalences are valuable as they provide the true burden of PTSD at a point in time. Moreover, 30-day prevalences are rarely reported because they require large sample sizes for estimation. In fact, 30-day prevalences have not previously been reported for WMH Survey countries.

Despite the debilitating nature of PTSD, many people with the disorder do not seek treatment, and even then do so only after experiencing symptoms for extended periods of time (Goldmann & Galea, 2014). In the USA, where services are more available than in most of the world (Roberts et al. 2011), only about half of those with PTSD seek treatment and only 58% of those seeking treatment receive care from a mental health professional (Kessler, 2000). Relatively little is known about treatment seeking by persons with PTSD outside the USA and Western Europe.

Several reviews and meta-analyses have examined correlates of PTSD, consistently finding that sociodemographic indicators of social disadvantage are associated with the disorder (Brewin et al. 2000; Tolin & Foa, 2006; Ozer et al. 2008). Younger age at the time of trauma has been associated with increased risk of developing PTSD (Brewin et al. 2000). Across a range of types of trauma exposure, women are approximately twice as likely as men to be diagnosed with PTSD (Tolin & Foa, 2006; Bangasser & Valentino, 2014). Individuals who have less social support, are less educated, and are of lower socioeconomic status are also more likely to be diagnosed (Brewin et al. 2000). However, the associations between demographic correlates and PTSD vary by study design (e.g. prospective v. retrospective), study population (e.g. civilian v. military) (Brewin et al. 2000), and country income level (Atwoli et al. 2015).

Moreover, few studies have examined sociodemographic correlates of PTSD persistence. Research on other disorders has shown differing associations of sociodemographic factors with disorder onset and course. For example, in the USA racial/ethnic minority status is associated with decreased risk of developing a substance-related disorder, but increased risk of the disorder is becoming chronic (Breslau et al. 2005). Also in the USA, major depressive disorder is less prevalent, but more likely to be chronic, among minority groups (Williams et al. 2007). For example, women are at higher risk of lifetime depression, but sex is unrelated to course of depression (Kessler, 2003).

While a number of country-specific results on the epidemiology of PTSD from the WMH Surveys have been published (Atwoli et al. 2013; Carmassi et al. 2014; Ferry et al. 2014; Kawakami et al. 2014; Olaya et al. 2015), this is the first paper to bring together WMH data cross-nationally in order to establish a global epidemiology of PTSD, including data on prevalence, treatment seeking, and demographic correlates. Specifically, this paper addressed four limitations of previous research. First, no previous report has brought together trauma exposure and PTSD prevalence rates across all the WMH Survey countries for summary and comparison. Second, the WMH Surveys addressed issues of study heterogeneity affecting cross-national prevalence estimates by using standardized methods for sample selection and assessment across all countries. Third, this report examines disparities in treatment-seeking by country income level. Fourth, this report examines whether sociodemographic correlates, extensively documented in the USA and European samples, are evident across country income levels.

Methods

Sample

The 26 WMH Surveys were conducted in 24 countries, 18 of which were nationally representative and eight that covered metropolitan areas with two surveys of distinct regions in both Spain and Colombia. They included four low-lower middle income countries, –six upper-middle income countries, and 13 high income countries as classified by the World Bank with surveys fielded between 2001 and 2012 (see online Supplemental Table S1). The surveys consisted of face-to-face interviews conducted in two parts. In part I of the interview, all respondents were evaluated for core psychiatric disorders. Part II of the interview, which assessed traumatic event (TE) exposure and PTSD, was administered to the subsample of respondents reporting any lifetime mental disorder as well as a probability subsample of part I respondents. Most surveys were composed of nationally representative household samples; several focused on all or select urban areas within a country. Sociodemographic information collected during interviews was used to post-stratify survey responses to create a nationally representative sample of each country with respect to these variables. A total of 123 299 respondents completed part I of the interview and 71 083 completed part II with an average response rate of 70.6% (range 45.9–97.2%). Institutional Review Boards at each organization conducting a survey approved the study and the informed consent procedure. A detailed description of the WMH Surveys is reported elsewhere (Heeringa et al. 2008).

Measures

The Composite International Diagnostic Interview (CIDI) version 3.0 was used to assess TE exposure, PTSD, and other psychiatric disorders according to DSM-IV criteria (Kessler & Üstün, 2004). The CIDI assessed 29 types of TEs across six categories: seven war-related events (e.g. combatant, civilian in a war zone), five types of physical assault (e.g. beaten by a caregiver as a child, mugged), three types of sexual assault (e.g. stalked, raped), six events involving other threats to physical integrity (e.g. life-threatening accidents, natural disasters), five events involving threats to loved ones (e.g. life-threatening illness/injury), and the traumatic death of loved one. In addition, respondents were asked an open-ended question about TEs not listed during the interview as well as TEs that respondents did not wish to describe in detail. Respondents were asked about both the number of lifetime occurrences and the age when each TE occurred (Benjet et al. 2016). Missing values on TE reports were assigned a value of ‘no’ and age of onset (AOO) was imputed using a single imputation based on the multiple imputation program in SAS 9.4. Respondents reporting more than one qualifying type of TE were assessed for PTSD twice: once for the self-nominated worst lifetime TE and a second time for one instance of a TE type randomly selected from all those reported (Breslau & Kessler, 2001). The number of TEs reported for the randomly selected TE was multiplied across all TEs, which were then aggregated across respondents and used to create a weighted dataset that was representative of all lifetime TEs that occurred to all respondents (Kessler & Üstün, 2004).

Respondents who experienced a qualifying TE (e.g. met Criterion A1) were assessed for DSM-IV PTSD Criteria B (re-experiencing), C (avoidance), and D (hyperarousal) regardless of whether they met the A2 requirement (response to the TE involved intense fear, helplessness or horror). Respondents meeting Criteria B-D were then assessed for Criteria E (symptom duration longer than 1 month) and F (clinically significant distress or impairment).

Six measures of PTSD prevalence were estimated: (1) prevalence of lifetime PTSD in the overall population, (2) prevalence of lifetime PTSD among the trauma exposed, (3) 12-month prevalence of PTSD among the exposed, (4) 30-day prevalence of PTSD among the exposed, (5) 12-month prevalence of PTSD among lifetime cases, and (6) 30-day prevalence of PTSD among 12-month cases. The 12-month and 30-day prevalence of PTSD among lifetime cases provide indirect estimates of both the reduction in PTSD symptoms as well as the persistence among those whose symptoms did not remit. Sociodemographic variables were also assessed at the time of interview, including age, gender, employment status (employed, student, homemaker, retired, employed), marital status (never married, divorced/separated/widowed, currently married), education level (no education, some primary, finished primary, some secondary, finished secondary, some college, finished college), and household income relative to national standards (low, low-average, high-average, high).

Statistical analyses

Cross-tabulations were used to calculate prevalence and treatment. Survival models were used to estimate the associations of correlates with TE exposure and with lifetime PTSD among the exposed, controlling for age-cohort, gender, person-years, and country. Associations between sociodemographic correlates and 12-month PTSD among lifetime cases were estimated using logistic regression controlling for time since PTSD onset, age of PTSD onset, sex, and country. Age of PTSD onset was defined separately within each country with the 25% of PTSD cases (25th percentile) with the earliest age were defined as early onset followed by early-average (50th percentile), late-average (75th percentile), and late onset. A continuous measure of time since onset was created by subtracting age at interview from the age when PTSD symptoms began.

Survival analysis was used to estimate AOO, defined as the respondent's age when they reported starting to have symptoms, and projected lifetime risk of PTSD. The actuarial method implemented in SAS 9.4 was used to generate the AOO curves. Significance was calculated using Wald and McNemar's χ2 tests. Because the data were weighted and clustered, the Taylor series linearization method implemented in the SUDAAN software package (11.0) was used to estimate design-based standard errors. Statistical significance was evaluated using two-sided tests, with p < 0.05 considered significant.

Results

Prevalence

The prevalence of trauma exposure and the prevalence of PTSD among the trauma exposed are presented in Table 1. TE exposure prevalence rates previously reported in Benjet et al. (2016) are included here to provide context for the PTSD data. The lifetime prevalence of PTSD in the population was 3.9% with significant variation across countries: High income countries (5.0%) had twice the proportion of PTSD cases as upper-middle income (2.3%) and lower-low middle income countries (2.1%).

Table 1. Prevalence of DSM-IV posttraumatic stress disorder (PTSD) in the World Mental Health surveys (N = 71 083)

a Region of the Americas (Colombia, Mexico, Brazil, Peru, The United States, Medellin); African region (South Africa); Western Pacific region (PRC Beijing and Shanghai, Japan, Australia,New Zealand); Eastern Mediterranean region (Israel, Iraq, Lebanon); Western European region (Belgium, France, Germany, Italy, The Netherlands, Spain, Northern Ireland, Portugal, Murcia); Eastern European region (Romania, Bulgaria, Ukraine).

b χ2 test of homogeneity to determine if there is variation in prevalence estimates across countries.

Among respondents who experienced a TE, the lifetime prevalence of PTSD was 5.6% and varied significantly across countries, income groups, and World Health Organization (WHO) regions, with lifetime prevalence of PTSD higher among trauma-exposed individuals in high-income countries (6.9%) than in upper-middle income (3.9%), and low-lower middle income countries (3.0%). A similar pattern was observed for 12-month and 30-day prevalence among the exposed. The 12-month prevalence among the exposed was 2.8% and varied significantly by country income, with the prevalence in high-income countries (3.6%) more than twice that in upper-middle (1.6%) and lower-low middle income countries (1.5%). The 30-day prevalence among the exposed was 1.4% and varied significantly by country income, with the prevalence in high-income countries (1.9%) almost three times that of upper-middle countries (0.7%) and lower-low middle income countries (0.6%).

Twelve-month prevalence among the exposed also varied across WHO regions, with the Western Pacific region reporting a rate (4.3%) more than four times the prevalence in the Africa region (1.0%). Thirty-day prevalence among the exposed also varied across WHO regions, with the Western Pacific region reporting a 30-day prevalence among the exposed (2.4%) that was 12 times the prevalence in the Africa region (0.2%).

Symptom persistence and reduction

The 12-month prevalences among lifetime cases and 30-day prevalences of PTSD among 12-month cases are presented in Table 2. The 12-month prevalence of PTSD among lifetime cases, which is one indicator of symptom persistence or reduction of PTSD among respondents who ever develop the disorder, varied by country, country income group, and WHO region. The proportion of cases with persistent PTSD varied widely across countries, even countries with similar lifetime prevalence. For example, Belgium and Lebanon had a similar lifetime prevalence of PTSD among the exposed of 4.1% and 4.2% respectively. However, the 12-month prevalence of PTSD among the exposed in Lebanon was twice (2.4%) that of Belgium's (1.2%). As a result, Lebanon's 12-month prevalence of PTSD among lifetime cases (58.2%) was more than twice that of Belgium's (28.0%).

Table 2. Prevalence of Persistent DSM-IV posttraumatic stress disorder (PTSD) in the World Mental Health surveys (N = 71 083)

a Region of the Americas (Colombia, Mexico, Brazil, Peru, The United States, Medellin); African region (South Africa); Western Pacific region (PRC Beijing and Shanghai, Japan, Australia,New Zealand); Eastern Mediterranean region (Israel, Iraq, Lebanon); Western European region (Belgium, France, Germany, Italy, The Netherlands, Spain, Northern Ireland, Portugal, Murcia); Eastern European region (Romania, Bulgaria, Ukraine).

b χ2 test of homogeneity to determine if there is variation in prevalence estimates across countries.

The 30-day prevalence among 12-month cases provides insight into how the duration of PTSD varies across countries. Of note, the 30-day prevalence of PTSD among 12-month cases varied significantly by country and WHO region, but not by country income. Again using the example of Lebanon and Belgium, Lebanon's 30-day prevalence of PTSD among the exposed (1.5%) was five times that of Belgium (0.3%). In other words, PTSD was five times more likely to persist over the year in Lebanon than in Belgium. In summary, Lebanon had a higher burden of PTSD than Belgium at the time of the survey, even though lifetime prevalence of PTSD among the exposed was similar across the two countries.

Age of onset

Cumulative distributions for the age of PTSD onset stratified by county income group are presented in Fig. 1. Onset of PTSD was earlier on average in high income countries than in low-lower and upper-middle income countries, with half of high income countries’ respondents reporting PTSD onset before age 30 compared with age 43 for low-lower income countries. In high income countries, 30% of respondents reported PTSD onset before age 18 compared with fewer than 16% in upper-middle income and 10% in low-lower income countries. Across all groups, the vast majority of respondents reported symptoms beginning immediately after the TE.

Fig. 1. Age of onset distributions of DSM-IV posttraumatic stress disorder by income-group countries.

Treatment

Fewer than half of respondents with 12-month PTSD reported seeking any type of treatment (see Table 3). Individuals in high income countries were approximately twice as likely to seek treatment (53.5%) as those in low-lower middle income (22.8%) and upper-middle income countries (28.7%). These disparities were observed across all treatment sectors. The one exception was the human services sector – including religious or spiritual advisors, social workers, and counselors – where treatment was sought less in upper-middle income countries (2.5%) than in low-lower income (7.1%) and high income countries (7.0%). While a quarter of respondents with PTSD reported seeking specialty mental health treatment in the 12 months before interview (see Fig. 2), there were substantial differences across country income groups, with only 3.2% of respondents in low-lower income countries receiving treatment compared with 28.7% in high income countries.

Fig. 2. Percentage of respondents reporting specialty mental health treatment by country income level.

Table 3. Among those with 12-month DSM-IV posttraumatic stress disorder, percent reporting treatment in the past 12 months (N = 71 083)

*p < 0.001.

a χ2 test of homogeneity to determine if there is variation in prevalence of treatment estimates across countries. χ2 test is only generated where there is more than one stable cell (>=5 cases).

b The mental health specialist sector, which includes psychiatrist and non-psychiatrist mental health specialists (psychiatrist, psychologist or other non-psychiatrist mental health professional; social worker or counselor in a mental health specialty setting; use of a mental health helpline; or overnight admissions for a mental health or drug or alcohol problems, with a presumption of daily contact with a psychiatrist).

c The general medical sector (general practitioner, other medical doctor, nurse, occupational therapist or any healthcare professional).

d The mental health specialist sector or the general medical sector.

e The human services sector (religious or spiritual advisor or social worker or counselor in any setting other than a specialty mental health setting).

f The CAM (complementary and alternative medicine) sector (any other type of healer such as herbalist or homeopath, participation in an internet support group, or participation in a self-help group).

g The human services sector or CAM.

h Respondents who sought any form of professional treatments listed in the footnotes above.

Sociodemographic correlates

Table 4 presents associations between sociodemographic correlates and TE exposure, lifetime PTSD among the exposed, and 12-month PTSD among lifetime cases in all countries. Sociodemographic results for TE exposure are presented for reference; the reader is referred to Benjet et al. (2016) for a detailed presentation and discussion (Benjet et al. 2016).

Table 4. Bivariate associations between sociodemographic correlates and DSM-IV posttraumatic stress disorder (PTSD) among trauma exposed (all countries combined N = 71 083)

*Significant at the 0.05 level, 2 sided test.

a These estimates are based on survival models adjusted for age-cohorts, gender, person-years and country.

b These estimates are based on logistic regression models adjusted for time since PTSD onset, age of PTSD onset, gender and country.

c χ2 test of significant differences between blocks of sociodemographic variables.

d Defined in terms of within-survey quartiles of the age-of-onset distribution.

e Denominator N: 71 083 = total sample; 1 646 308, 1 310 008 and 30 67 607 = number of person-years in the survival models; 4103 = number of lifetime cases of PTSD.

f Iraq is not included into the analysis related to exposure to traumatic events (TEs) because the age of first exposure to TEs is not available in Iraq. Excluding Iraq, there were 49 339 people exposed to TEs and 3963 people with PTSD.

All sociodemographic correlates were significantly associated with a lifetime diagnosis of PTSD among the trauma exposed. Respondents who were younger, female, not employed, not currently married, less educated, and having a lower household income were more likely to develop PTSD. However, female sex, marital status, and education level were not significantly associated with persistence defined as 12-month PTSD among lifetime cases. In addition, all household income categories below the highest income level were associated with lifetime PTSD, but only the lowest income category was associated with persistent PTSD. Being a homemaker, retired, or ‘other’ employment status were associated with an increased risk of lifetime PTSD compared with being employed, but only an employment status of ‘other’ was associated with persistent PTSD.

Sociodemographic results by country income level are presented in online Supplemental Tables S2–S4. Results were largely consistent for lifetime PTSD among the exposed across income level with three differences. First, lower education was not associated with PTSD prevalence in upper-middle income countries, but was associated in the low-lower and high income country groups. Second, younger respondents were not more likely to develop PTSD in low-lower income and upper-middle income country groups. Third, there were no significant differences by employment status for the risk of PTSD in the low-lower and upper-middle income country groups although ‘other’ employment was still associated with PTSD onset in the upper-middle income country group. For 12-month PTSD among lifetime cases, sociodemographic results differed markedly between the high income country group and the other two groups. No sociodemographic variables were associated with persistent PTSD in the low-lower and upper-middle income country groups. In contrast, having lower household income, ‘other’ employment status, and being divorced, separated, or widowed were associated with more persistent PTSD in the high income country group.

Discussion

Study limitations

The WMH Surveys have four limitations with particular relevance for interpreting results about trauma exposure and PTSD. First, substantial variation in the response rate across countries (45.9–97.2%) may lead to bias if trauma or other sociodemographic variables affected the likelihood of non-response. To account for possible non-response bias, we used collected sociodemographic information and population data to post-stratify each country's sample to be representative of the population. Second, TE exposure and PTSD were assessed retrospectively, which may have led to underreporting of lifetime TE exposure and PTSD or misestimation of AOO. Third, while the WMH surveys used the same assessment in all countries, cultural differences may have affected respondents’ willingness to discuss sensitive issues, especially stigmatizing TEs. We attempted to mitigate underreporting by including an open-ended question on TEs that respondents did not want to describe, which was endorsed by 6.1% of the total sample. Fourth, the WMH Surveys did not include many countries with recent mass violence and armed conflict. The limited data available suggest that rates of PTSD are much higher rates in communities exposed to mass violence [e.g. lifetime PTSD prevalence rates of 37.4% in Algeria (De Jong et al. 2001)].

Study strengths and notable findings

Despite these limitations, the WMH Surveys have several strengths. First, these surveys assessed a large sample within each country, two-thirds of which were nationally representative. Their samples were sufficiently large to permit estimates of 30-day prevalence in addition to 12-month and lifetime prevalence of PTSD. For many countries, these are the first published 30-day prevalence estimates of PTSD, providing important information on the burden of PTSD. An additional strength was the use of standardized measures to assess TEs and PTSD across all countries. Our use of uniform questions mitigates differences due to variation in wording and operationalization of traumatic experiences and reactions. In addition, we collected detailed, standardized demographic information for all respondents, enabling us to examine the associations of individual- and social-level factors with PTSD prevalence and persistence.

Four notable findings merit discussion. First, we found that 5.6% of respondents who were exposed to trauma had a lifetime diagnosis of PTSD, with prevalence ranging from 0.5% to 14.5% across countries, which may stem from variation in TE types across countries. Liu et al. (2017) found that PTSD prevalence was associated with type of TE and that interpersonal TEs (e.g. sexual violence) conferred an increased risk for PTSD onset (Liu et al. 2017). Half of respondents with the lifetime disorder had symptoms in the last 12 months, and almost half of 12-month cases reported symptoms in the 30 days before interview, suggesting a high level of symptom persistence. It is likely that at least some participants with and without 30-day PTSD experienced relapsing and remitting symptoms over the year, a course of PTSD that has been documented in several longitudinal studies (Osenbach et al. 2014; Bryant et al. 2015). The DSM system, however, does not distinguish between those who fully remit and those whose symptoms are sensitive to flaring up again with reminders. Consequently, the 30-day prevalence of PTSD, which represents the burden of PTSD at the specific time the survey was conducted, may underestimate the burden of PTSD if participants symptoms had waned and were below the threshold for a formal PTSD diagnosis at the time of interview, but were still in distress. Similarly, the burden of PTSD may be overestimated if symptoms were waxing at the time of interview leading to more individuals meeting formal diagnostic criteria than otherwise would.

Second, our findings are also among the first reports of treatment seeking for PTSD in countries outside of the USA and Western Europe. Across all countries, only half of all respondents reported seeking any type of treatment. We found that respondents in high income countries were almost twice as likely to seek treatment as those in low-lower middle and upper-middle income countries. These results broaden the findings from a previous WMH report of 15 countries, which found significant variation in treatment during the year of disorder onset with 0.8% to 36.4% of respondents reporting treatment for anxiety disorders and a median delay of 3–30 years before treatment contact (Wang et al. 2007).

Third, our results confirm earlier reports that PTSD onset occurs later than in life than other anxiety and mood disorders (Kessler et al. 2005; Kessler et al. 2007). However, we found wide variation in age of onset across countries and income groups, with PTSD developing significantly earlier in high income countries (median age 25–28) compared with low-lower middle (median age 43) and upper-middle income countries (median age 30). Interestingly, the relatively late AOO of PTSD contrasts with an earlier WMH report showing that incident TE exposure is more common among children, adolescents, and young adults than among older individuals (Benjet et al. 2016). While this may imply that conditional risk for developing PTSD is higher in older adults exposed to trauma, results presented in Table 4 show that younger respondents were at greater risk for developing PTSD. One possible reason for this discrepancy may be that younger people are more likely to be exposed to the types of TEs that have greater risk for the development of PTSD. Exploring this issue is beyond the scope of this chapter but we plan to address it in future analyses of WMH data.

Fourth, we also examined sociodemographic correlates of PTSD prevalence and persistence. We found that lifetime PTSD among the exposed was associated with being younger, female, not employed, not currently married, having a lower education level, and a lower household income. These results were mostly consistent across country income groups. Moreover, our results for female sex are consistent with a large literature on sex differences in risk for PTSD (Tolin & Foa, 2006). Only income level and employment status were associated with persistent PTSD in the overall sample. When countries were stratified by country income, no sociodemographic variables were correlated with persistent PTSD in the low-lower middle and upper-middle country groups, whereas lower socioeconomic status was associated with persistent PTSD in the high income country group. Given lack of information on the temporal ordering of sociodemographic factors and PTSD onset, we cannot determine whether factors such as marital status or socioeconomic status are risk factors for, or consequences of, the disorder.

Conclusions

The WMH Surveys show that half of PTSD cases are persistent and that, among respondents reporting PTSD symptoms in the last 12 months, only half received any type of treatment. The gap in treatment is even larger in low-lower middle income countries and upper-middle income countries, where only a quarter of respondents reported any kind of treatment. Our results suggest at least two targets for intervention.

The first is to reduce the psychological sequelae of trauma by early identification of those at risk for the disorder. PTSD symptoms typically begin shortly after TE exposure and evolve with time to either persistence or recovery. PTSD is one of the most preventable mental disorders, as many people exposed to TEs come to clinical attention in first response settings such as emergency rooms, intensive care units, and trauma centers. Controlled clinical trials show that PTSD risk can be significantly reduced by early preventive interventions (Foa et al. 1995; Kearns et al. 2012; Shalev et al. 2012). However, these interventions have nontrivial costs, making it infeasible to offer them to all persons exposed to TEs given that only a small minority goes on to develop PTSD (Kessler et al. 1995; Kessler, 2000; Roberts et al. 2010). They are also unnecessary for many survivors who recovery spontaneously (Shalev et al. 2012). To be cost-effective, risk prediction rules are needed to identify, which exposed persons are at high risk of PTSD taking into consideration that predictors may vary between samples (Andrews et al. 2000; Brewin et al. 2000; Brewin, 2005; Roberts et al. 2011), within samples (e.g. between male and female survivors), and at different time lags from the TE (Shalev et al. 1997; Freedman et al. 1999). Data-driven methods such as machine learning have shown promise in identifying persons at high risk for developing PTSD (Kessler et al. 2014). However, large-scale prospective studies of trauma survivors are needed to develop predictive algorithms that can be widely used. One such study has just been initiated by the National Institutes of Mental Health.

A second strategy is to improve the identification and access to treatment for persons with PTSD. The low reported rates of treatment seeking was striking across all country income levels but particularly so among the low-lower middle and upper-middle income countries, where treatment has been shown to be effective (Bass et al. 2013). Screening for trauma and PTSD in primary care may improve identification and aid in treatment referral. Health care organizations such as Kaiser Permanente have launched major trauma informed care initiatives toward this goal (Sharp, 2015). Moreover, treatment of PTSD in primary settings has been shown to be effective (Roy-Byrne et al. 2010). However, major efforts to such as PRIME (program for improving mental health care), which is focused on improving mental health care in several low and middle income countries through integration with maternal and primary care have not, to date, included PTSD as a target disorder (Lund et al. 2012). Thus, much work remains to be done with regard to policy, research and treatment to address issues of access to care and decrease the global burden of PTSD.

Supplementary material

For supplementary material accompanying this paper visit https://doi.org/10.1017/S0033291717000708.

Acknowledgements

The World Health Organization World Mental Health (WMH) Survey Initiative is supported by the National Institute of Mental Health (NIMH; R01 MH070884 and R01 MH093612-01), the John D. and Catherine T. MacArthur Foundation, the Pfizer Foundation, the US Public Health Service (R13-MH066849, R01-MH069864, and R01 DA016558), the Fogarty International Center (FIRCA R03-TW006481), the Pan American Health Organization, Eli Lilly and Company, Ortho-McNeil Pharmaceutical, Inc., GlaxoSmithKline, and Bristol-Myers Squibb. We thank the staff of the WMH Data Collection and Data Analysis Coordination Centres for assistance with instrumentation, fieldwork, and consultation on data analysis. None of the funders had any role in the design, analysis, interpretation of results, or preparation of this paper. The 2007 Australian National Survey of Mental Health and Wellbeing is funded by the Australian Government Department of Health and Ageing. The São Paulo Megacity Mental Health Survey is supported by the State of São Paulo Research Foundation (FAPESP) Thematic Project Grant 03/00204-3. The Bulgarian Epidemiological Study of common mental disorders EPIBUL is supported by the Ministry of Health and the National Center for Public Health Protection. The Chinese World Mental Health Survey Initiative is supported by the Pfizer Foundation. The Colombian National Study of Mental Health (NSMH) is supported by the Ministry of Social Protection. The Mental Health Study Medellín – Colombia was carried out and supported jointly by the Center for Excellence on Research in Mental Health (CES University) and the Secretary of Health of Medellín.The ESEMeD project is funded by the European Commission (Contracts QLG5-1999-01042; SANCO 2004123, and EAHC 20081308), [the Piedmont Region (Italy)], Fondo de Investigación Sanitaria, Instituto de Salud Carlos III, Spain (FIS 00/0028), Ministerio de Ciencia y Tecnología, Spain (SAF 2000-158-CE), Departament de Salut, Generalitat de Catalunya, Spain, Instituto de Salud Carlos III (CIBER CB06/02/0046, RETICS RD06/0011 REM-TAP), and other local agencies and by an unrestricted educational grant from GlaxoSmithKline. Implementation of the Iraq Mental Health Survey (IMHS) and data entry were carried out by the staff of the Iraqi MOH and MOP with direct support from the Iraqi IMHS team with funding from both the Japanese and European Funds through United Nations Development Group Iraq Trust Fund (UNDG ITF). The Israel National Health Survey is funded by the Ministry of Health with support from the Israel National Institute for Health Policy and Health Services Research and the National Insurance Institute of Israel. The World Mental Health Japan (WMHJ) Survey is supported by the Grant for Research on Psychiatric and Neurological Diseases and Mental Health (H13-SHOGAI-023, H14-TOKUBETSU-026, H16-KOKORO-013,H25-SEISHIN-IPPAN-006 from the Japan Ministry of Health, Labour and Welfare. The Lebanese Evaluation of the Burden of Ailments and Needs Of the Nation (L.E.B.A.N.O.N.) is supported by the Lebanese Ministry of Public Health, the WHO (Lebanon), National Institute of Health / Fogarty International Center (R03 TW006481-01), anonymous private donations to IDRAAC, Lebanon, and unrestricted grants from, Algorithm, AstraZeneca, Benta, Bella Pharma, Eli Lilly, Glaxo Smith Kline, Lundbeck, Novartis, Servier, Phenicia, UPO. The Mexican National Comorbidity Survey (MNCS) is supported by The National Institute of Psychiatry Ramon de la Fuente (INPRFMDIES 4280) and by the National Council on Science and Technology (CONACyT-G30544- H), with supplemental support from the PanAmerican Health Organization (PAHO). Te Rau Hinengaro: The New Zealand Mental Health Survey (NZMHS) is supported by the New Zealand Ministry of Health, Alcohol Advisory Council, and the Health Research Council. The Northern Ireland Study of Mental Health was funded by the Health & Social Care Research & Development Division of the Public Health Agency. The Peruvian World Mental Health Study was funded by the National Institute of Health of the Ministry of Health of Peru. The Portuguese Mental Health Study was carried out by the Department of Mental Health, Faculty of Medical Sciences, NOVA University of Lisbon, with collaboration of the Portuguese Catholic University, and was funded by Champalimaud Foundation, Gulbenkian Foundation, Foundation for Science and Technology (FCT) and Ministry of Health. The Romania WMH study projects ‘Policies in Mental Health Area’ and ‘National Study regarding Mental Health and Services Use’ were carried out by National School of Public Health & Health Services Management (former National Institute for Research & Development in Health), with technical support of Metro Media Transilvania, the National Institute of Statistics-National Centre for Training in Statistics, SC. Cheyenne Services SRL, Statistics Netherlands and were funded by Ministry of Public Health (former Ministry of Health) with supplemental support of Eli Lilly Romania SRL. The South Africa Stress and Health Study (SASH) is supported by the US National Institute of Mental Health (R01-MH059575) and National Institute of Drug Abuse with supplemental funding from the South African Department of Health and the University of Michigan. The Psychiatric Enquiry to General Population in Southeast Spain – Murcia (PEGASUS-Murcia) Project has been financed by the Regional Health Authorities of Murcia (Servicio Murciano de Salud and Consejería de Sanidad y Política Social) and Fundación para la Formación e Investigación Sanitarias (FFIS) of Murcia. The Ukraine Comorbid Mental Disorders during Periods of Social Disruption (CMDPSD) study is funded by the US National Institute of Mental Health (RO1-MH61905). The US National Comorbidity Survey Replication (NCS-R) is supported by the National Institute of Mental Health (NIMH; U01-MH60220) with supplemental support from the National Institute of Drug Abuse (NIDA), the Substance Abuse and Mental Health Services Administration (SAMHSA), the Robert Wood Johnson Foundation (RWJF; Grant 044708), and the John W. Alden Trust. Dr Stein is supported by the Medical Research Council of South Africa (MRC). A complete list of all within-country and cross-national WMH publications can be found at http://www.hcp.med.harvard.edu/wmh/.

The WHO World Mental Health Survey collaborators are Sergio Aguilar-Gaxiola, M.D., Ph.D., Ali Al-Hamzawi, M.D., Mohammed Salih Al-Kaisy, M.D., Jordi Alonso, M.D., Ph.D., Laura Helena Andrade, M.D., Ph.D., Corina Benjet, PhD, Guilherme Borges, ScD, Evelyn J. Bromet, Ph.D., Ronny Bruffaerts, Ph.D., Brendan Bunting, Ph.D., Jose Miguel Caldas de Almeida, M.D., Ph.D., Graca Cardoso, M.D., Ph.D., Somnath Chatterji, M.D., Alfredo H. Cia, M.D., Louisa Degenhardt, Ph.D., Koen Demyttenaere, M.D., Ph.D., John Fayyad, M.D., Silvia Florescu, M.D., Ph.D., Giovanni de Girolamo, M.D., Oye Gureje, Ph.D., DSc, FRCPsych, Josep Maria Haro, M.D., Ph.D., Yanling He, M.D., Hristo Hinkov, M.D., Chi-yi Hu, Ph.D., M.D., Yueqin Huang, M.D., MPH, Peter de Jonge, Ph.D., Aimee Nasser Karam, Ph.D., Elie G. Karam, M.D., Norito Kawakami, M.D., DMSc, Ronald C. Kessler, Ph.D., Andrzej Kiejna, M.D., Ph.D., Viviane Kovess-Masfety, M.D., Ph.D., Sing Lee, MB, BS, Jean-Pierre Lepine, M.D., Daphna Levinson, Ph.D., John McGrath, M.D., Ph.D., Maria Elena Medina-Mora, Ph.D., Jacek Moskalewicz, DrPH, Fernando Navarro-Mateu, M.D., Ph.D., Beth-Ellen Pennell, MA, Marina Piazza, MPH, Sc.D., Jose Posada-Villa, M.D., Kate M. Scott, Ph.D., Tim Slade, Ph.D., Juan Carlos Stagnaro, M.D., Ph.D., Dan J. Stein, FRCPC, Ph.D., Margreet ten Have, Ph.D., Yolanda Torres, MPH, Dra.HC, Maria Carmen Viana, M.D., Ph.D., Harvey Whiteford, Ph.D., David R. Williams, MPH, Ph.D., Bogdan Wojtyniak, Sc.D.

Declaration of Interest

In the past 3 years, Dr Kessler received support for his epidemiological studies from Sanofi Aventis, was a consultant for Johnson & Johnson Wellness and Prevention, and served on an advisory board for the Johnson & Johnson Services Inc. Lake Nona Life Project. Kessler is a co-owner of DataStat, Inc., a market research firm that carries out healthcare research.

In the past 3 years, Dr Stein has received research grants and/or consultancy honoraria from AMBRF, Biocodex, Cipla, Lundbeck, National Responsible Gambling Foundation, Novartis, Servier, and Sun.

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