Cross-national associations between gender and mental disorders in the WHO World Mental Health Surveys

Context—Gender differences in mental disorders, including more anxiety-mood disorders among women and more externalizing disorders among men, are found consistently in epidemiological surveys. The “gender roles” hypothesis suggests that these differences should narrow as the roles of women and men become more equal. Objective—To study time-space (i.e., cohort-country) variation in gender differences in lifetime DSM-IV mental disorders across cohorts in 15 countries in the WHO World Mental Health (WMH) Survey Initiative and determine if this variation is significantly related to time-space variation in female gender role traditionality (GRT) as measured by aggregate patterns of female education, employment, marital timing, and use of birth control. Design/Setting and Participants—Face-to face household surveys of 72,933 communitydwelling adults in Africa, the Americas, Asia, Europe, the Middle East, and the Pacific. Main Outcomes—The WHO Composite International Diagnostic Interview (CIDI) assessed lifetime prevalence and age-of-onset of 18 DSM-IV anxiety, mood, externalizing, and substance disorders. Survival analyses estimated time-space variation in Female:Male (F:M) odds-ratios (ORs) of these disorders across cohorts defined by age ranges 18–34, 35–49, 50–64, and 65+. Structural equation analysis examined predictive effects of variation in GRT on these ORs. Results—Women had more anxiety-mood disorders than men and men more externalizingsubstance disorders than women in all cohorts and countries. Although gender differences were generally consistent across cohorts, significant narrowing was found in recent cohorts for major depressive disorder (MDD) and substance disorders. This narrowing was significantly related to temporal (MDD) and spatial (substance disorders) variation in GRT. Conclusion—While gender differences in most lifetime mental disorders were fairly stable over the time-space units studied, substantial inter-cohort narrowing of differences in major depression was found related to changes in the traditionality of female gender roles. Further research is needed to understand why this temporal narrowing was confined to major depression. Epidemiological surveys have consistently documented significantly higher rates of anxiety and mood disorders among women than men1, 2 and significantly higher rates of externalizing and substance use disorders among men than women.3–5 Although a number of biological, psychosocial, and biopsychosocial hypotheses have been proposed to account for these patterns,6–8 evidence that gender differences in depression9, 10 and substance use11–13 have narrowed in a number of countries has led to a special interest in the “gender roles” hypothesis. The latter asserts that gender differences in the prevalence of mental disorders are due to differences in the typical stressors, coping resources, and opportunity structures for expressing psychological distress made available differentially to women and men in different countries at different points in history.14, 15 Consistent with this hypothesis, evidence of decreasing gender differences in depression and substance use has been found largely in countries where the roles of women have improved in terms of opportunities for employment, access to birth control, and other indicators of increasing gender role equality, while trend studies in countries where gender roles have been more static11, 16 or over periods of historical time when gender role changes have been small17 have failed to document a reduction in gender differences in depression or substance use. Most research aimed at investigating the gender roles hypothesis has focused on individuallevel variation in roles in a single country at a single point in time.18–20 This approach is limited in three ways. First, selection bias into roles due to pre-existing mental illness (e.g., women with agoraphobia having a higher probability than other women of becoming homemakers rather than seeking employment outside the home) confounds attempts to evaluate the causal effects of gender roles. Second, gender differences are largely confined to differences Seedat et al. Page 2 Arch Gen Psychiatry. Author manuscript; available in PMC 2010 January 22. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript in lifetime risk, with much less evidence for gender differences in recent prevalence among lifetime cases.21 This means that investigation of the determinants of gender difference should focus on lifetime first onset rather than on the recent prevalence that has been the focus of most studies. Third, as the gender roles hypothesis is a hypothesis about the effects of social context, a rigorous test of the hypothesis requires an analysis of societal-level time-space variation rather than analysis of the individual-level variation that has been the focus of most studies. A small number of cross-national comparative studies have examined spatial variation in gender differences in depression22 and alcohol abuse13 at a point in time or, more rarely, at two points in time.11 Although these studies raised the possibility that gender roles might be associated with variation in the magnitude of gender differences in these outcomes, they were unable to test this hypothesis due to the small number of cross-sectional country-level observations included in the analyses. The current report provides a more direct test of the gender roles hypothesis by analyzing community epidemiological data collected from respondents surveyed in 15 countries as part of the World Health Organization (WHO) World Mental Health (WMH) Survey Initiative.21 Previous cross-national comparisons of gender differences in mental illness focused on cross-sectional differences. We, in comparison, use retrospective reports obtained in the WMH surveys about lifetime occurrence and age-of-onset of mental disorders in different birth cohorts to study time-space variation in lifetime risk. Specifically, we examine both variation across cohorts within a single country (i.e., temporal variation) and variation across countries within a single cohort (i.e., special variation) in lifetime risk of mental disorders as a function of time-space variation in the traditionality of gender roles. Lifetime risk is the focus rather than recent prevalence even though accuracy of reporting is doubtlessly better for recent episodes than lifetime occurrence in order to address the fact that gender differences in lifetime risk are much more robust than gender differences in current prevalence among lifetime cases METHODS Sample WMH surveys were carried out in samples of adults (ages 18+) in five countries classified by the World Bank23 as developing (Colombia, Lebanon, Mexico, South Africa, Ukraine) and ten classified as developed (Belgium, France, Germany, Israel, Italy, Japan, Netherlands, New Zealand, Spain, and United States of America). The total sample size was 72,933. Individual country samples ranged from 2,372 (Netherlands) to 12,790 (New Zealand). (Table 1) The weighted average response rate was 71.2%. Country-specific response rates ranged from 45.9% (France) to 87.7% (Colombia). All surveys were based on probability household samples either regionally representative (Colombia, Japan, and Mexico) or nationally representative (other countries). Survey sample characteristics are described in more detail elsewhere.24 All interviews were conducted face-to-face by trained lay interviewers. Each interview had two parts. All respondents completed Part I, which contained assessments of core mental disorders, while all Part I respondents who met criteria for any core disorder plus a probability sub-sample of approximately 25% of other Part I respondents were administered Part II. Part II assessed correlates, service use, and disorders of secondary interest. The Part II data, used in the current report, were weighted to adjust for over-sampling Part I respondents with mental disorders, for differential probabilities of selection within households (due to only one household member, and in some cases two, being surveyed in each household no matter the number of adults residing in the household), and to match sample distributions to population socio-demographic distributions. Standardized interviewer training procedures, translation and back-translation procedures, and quality control procedures were applied across all WMH countries to ensure comparability. Informed consent was obtained in all countries. These procedures are described in more detail elsewhere.24, 25 Seedat et al. Page 3 Arch Gen Psychiatry. Author manuscript; available in PMC 2010 January 22. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript DSM-IV disorders Mental disorders were assessed with Version 3.0 of the WHO Composite International Diagnostic Interview (CIDI),26 a fully-structured diagnostic interview. Translation, backtranslation, and harmonization of the interview in local languages with the original English language version of CIDI 3.0 were carried out in each WMH country using WHO guidelines. 27 Disorders were assessed using the definitions of the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). 28 Disorders assessed included mood disorders (major depressive disorder, dysthymic disorder, bipolar disorder), anxiety disorders (panic disorder, generalized anxiety disorder, agoraphobia without panic disorder, social phobia, specific phobia, separation anxiety disorder, post-traumatic stress disorder), externalizing disorders (attention-deficit/hyperactivity disorder, conduct disorder, intermittent explosive disorder, oppositional-defiant disorder), and substance disorders (alcohol and illicit drug abuse with or without dependence). DSM-IV organic exclusion rules were used to make diagnoses. Methodological evidence collected in clinical reappraisal studies show that diagnos