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Objective: Most research on the association between sleep disturbances and depression has looked at cross-sectional data. The authors used two waves of data from a panel study of community residents aged 50 years or more to investigate this issue prospectively. Method: Data on symptoms of major depressive episodes and sleep problems were examined for a subgroup of the 1994 and 1995 surveys of the Alameda County (California) Study (N=2,370). The authors examined the effects of age, gender, education, marital status, social isolation, functional impairment, financial strain, and alcohol use. Depression was measured with 12 items that covered the DSM-IV diagnostic criteria for major depressive episodes, including insomnia and hypersomnia. Results: The prevalences were 23.1% for insomnia and 6.7% for hypersomnia in 1994. Sleep was a significant correlate of depression, as were being female, older age, social isolation, low education, financial strain, and functional impairment. When sleep problems and depression were examined prospectively, with controls for the effects of the other variables, sleep problems in 1994 predicted depression in 1995. However, other symptoms of major depressive episodes - anhedonia, feelings of worthlessness, psychomotor agitation/retardation, mood disturbance, thoughts of death - were much stronger predictors of future major depression. Conclusions: Sleep disturbance and other symptoms that are diagnostic for major depression are strongly associated with the risk of future depression. Sleep disturbance appears to be a less important predictor of depression. More epidemiologic research is needed on the relative contributions of the range of depressive symptoms to the risk of clinical depression.

Objective: This study was done to update and expand information given in recent reviews, provide a more systematic critique of past research, identify current research trends and issues, and explore possible strategies for future research in child psychiatric epidemiology. Method: The authors identified and reviewed 52 studies done over the past four decades that attempted to estimate the overall prevalence of child and adolescent psychiatric disorders. Results: About as many studies have been published since 1980 as were published before. Sample sizes ranged from 58 to 8,462; most were in the 500-1,000 range. Studies were carried out in over 20 countries, most frequently the United States and the United Kingdom. Subjects' ages ranged from 1 to 18 years. Rutter's criteria were the most frequently used for case definition; more recent studies were more likely to use DSM criteria. The most frequently used interview was the Rutter schedule. The most common time frame for calculating prevalence was the present, followed by 6 months and 1 year. Prevalence estimates of psychopathology ranged from approximately 1% to nearly 51% (mean = 15.8%). Median rates were 8% for preschoolers, 12% for preadolescents, 15% for adolescents, and 18% in studies including wider age ranges. Conclusions: The evidence is less informative than expected because of several problems that continue to plague research on child and adolescent disorders. These involve sampling, case ascertainment, case definition, and data analyses and presentation. Progress in understanding the epidemiology of child disorders will largely depend on whether future research successfully meets these challenges.