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Cumulative incidence of depression in 1,045 men according to sleep complaints in medical school—a) insomnia (○) versus no insomnia (D); b) difficulty sleeping under stress (○) versus no difficulty (D). The numbers below each Kaplan-Meier plot are the numbers of men included in the analysis at each time point.
Reproduced with permission. Chang et al. Insomnia in young men and subsequent depression: The Johns Hopkins Study Precursors. Am J Epidemiol. 1997;146(2):105–114.
