Reevaluation of secular trends in depression rates

Results of numerous community surveys of psychiatric illness suggest a striking change in the occurrence of depression, with younger generations experiencing higher lifetime risk and earlier age of onset. Data from the National Institute of Mental Health Epidemiologic Catchment Area Survey (a cross-sectional survey of psychiatric morbidity in five US communities conducted between 1980 and 1984) were reexamined for evidence of methods effects which might contribute to these unexpected findings. A pattern of higher lifetime risk and earlier age of onset among recent birth cohorts was observed for every psychiatric disorder examined, with schizophrenia, major depression, and panic disorder showing equally strong trends. For respondents of all ages, reported first onset of major depression clustered in the 10-year period prior to the study interview, in contrast to the expectation that older respondents would report onset in early adulthood. Examination of individual psychiatric symptoms revealed a nearly universal pattern of decreasing lifetime prevalence among older respondents, a reversal of the expected accumulation of lifetime symptoms with age. These findings suggest that effects of study methods may contribute to the apparent temporal trends in prevalence of depression and that cross-sectional surveys may underestimate lifetime psychiatric morbidity among older respondents. Generational changes in the lifetime risk of depression or other psychiatric disorders may not be reliably assessed by cross-sectional survey data.