Changing trends in the prevalence of common mental disorders in Taiwan: a 20-year repeated cross-sectional survey

Background Macrosocial changes might affect mental health. We investigated whether the prevalence of common mental disorders (CMDs) changed over a 20-year period of industrialisation in Taiwan. Methods We used the 12-item Chinese Health Questionnaire to assess mental status of Taiwanese adults in 1990, 1995, 2000, 2005, and 2010. Respondents with scores of 3 or higher were classified as having probable CMDs. We assessed trends of probable CMDs with the Cochran-Armitage test and their risk factors (sex, age, marital status, educational level, employment status, and physical health) with multivariable logistic regression. The trends were compared with national rates of unemployment, divorce, and suicide. Findings Of 10 548 respondents, 9079 (86.1%) completed questionnaires. The prevalence of probable CMDs doubled from 11.5% in 1990 to 23.8% in 2010 (time trend p<0.001). Increases paralleled rises in national rates of unemployment, divorce, and suicide at all five timepoints. Significant risk factors for probable CMDs were female sex (adjusted odds ratio 1.6, 95% CI 1.4-1.8), 6 or fewer years of education (1.3, 1.1-1.5), unemployment (1.4, 1.1-1.7), and poor physical health that limited daily activities (6.5, 5.4-8.0). When we controlled for these factors in multivariable models, the time trends remained significant (p<0.0001). Interpretation National rates of unemployment, divorce, and suicide increased in parallel with prevalence of probable CMDs in Taiwan. Therefore, clinical and social preventive measures both seem important during times of change to the economy and labour market.