To examine the role of genetic and familialenvironmental factors in the origin of stressful life events.
Self-report questionnaires describing stressful life events in the last year.
Both members of 2315 twin pairs ascertained from the population-based Virginia Twin Registry.
Life events were modestly but significantly correlated in twin pairs, and correlations in monozygotic (MZ) twins consistently exceeded those in dizygotic (DZ) twins. For total life events, the best-fitting twin model indicated that familial-environmental and genetic factors each accounted for around 20% of the total variance. Individual life events could be best divided into "network events" (directly affecting individuals in the respondent's socialnetwork) where twin resemblance was due solely to the familial environment, and "personal" events (directly affecting the response) where most twin resemblance was the result of genetic factors.
While neither genes nor familial environment is likely to directly produce life events, personal and social factors that predispose to life events are substantially influenced by an individual's genetic and family background. These results, which suggest that stressful life events reflect more than random influences, may have important implications for our understanding of the relationship between stressful life events and psychopathology.