A REGISTRY-BASED TWIN STUDY OF DEPRESSION IN MEN

Background: The only large, registry-based twin studs of depression us ing diagnostic criteria assessed by structured interview included only women. We present results from a comparable study of men. Methods: Da ta were collected using a standardized telephone interview of men from the Vietnam Era Twin Registry. Both twins from 3372 pairs participate d. Proband-wise concordance rates and biometric modeling were used to analyze the data. Results: The diagnosis of major depression (MB), as defined by DSM-III-R, and the subtype of severe/psychotic MD were sign ificantly affected by genetic (h(2)=0.36 and 0.39, respectively) and n onshared environmental (e(2)=0.64 and 0.61, respectively) factors but not by family environmental factors. Dysthymia and mild and moderate M D were affected by family environmental (c(2)=0.27, 0.08, and 0.14, re spectively) and nonshared environmental (e(2)=0.73, 0.92, and 0.86, re spectively) factors but not by genetic factors. Early-onset (before ag e 30 years) and late-onset (after age 30 years) MD were significantly affected by genetic (h(2)=0.47 and 0.10, respectively) and nonshared e nvironmental (e(2)=0.53 and 0.90, respectively) factors. Early-onset M D was significantly more heritable than late-onset MD. Conclusions: Th e magnitude of genetic and environmental effects on depression in men is similar to that previously reported in women. Also similar to previ ous findings, more severe and earlier-onset depression may be more str ongly affected by genetic factors, but differences in the reliability of reports of depression associated with severity may innate estimates of the effect of the unique environment and deflate heritability esti mates for less severe depression.