The Effect of Diagnostic Hierarchy in Genetic Epidemiological Studies of Psychiatric Disorders

I ported the rates of late-onset major depression (MD) (onset after 30 years of age) in relatives of subjects with panic disorder only, with panic disorder and MD, with earlyonset MD (onset before 30 years of age), and never mentally ill. By the definition of their diagnostic hierarchy, an individual with early-onset MD cannot have a diagnosis of lateonset MD. However, to compute the risk for late-onset MD, Weissman et al divided the number of relatives with lateonset MD by the total number of relative-years at risk in each group, including relatives with early-onset MD. One may argue that subj ects with early-onset MD should not be considered at risk for late-onset MD, since the diagnostic hierarchy used precludes making a diagnosis of late-onset MD in such subjects.² Therefore, the situation of subjects with early-onset MD is analogous to that of individuals in epidemiological studies who died or did