A multidimensional twin study of mental health in women.

OBJECTIVE While researchers have increasing insight into the role of genetic and environmental factors in the etiology of psychiatric and substance use disorders, they know much less about how such factors influence the dimensions of healthy psychological functioning. METHOD In a population-based sample of 794 female-female twin pairs, the authors examined, by using multivariate structural equation modeling, six dimensions of mental health: perceived physical health, nonconflictual interpersonal relationships, anxious-depressive symptoms, substance use, social support, and self-esteem. RESULTS The best-fit model was complex and constituted five common factors (two genetic, one family environmental, and two unique environmental); variable-specific genetic effects for physical health, substance use, and social support; and variable-specific family environmental effects for interpersonal relationships and substance use. Genetic effects were seen for all six dimensions; total heritabilities ranged from 16% to 49%. Family environment was an important influence on interpersonal relationships, substance use, and social support. CONCLUSIONS Mental health is a complex phenotype that is influenced by a diverse array of genetic and environmental factors. While genetic factors appear to be of moderate etiologic importance in all major dimensions of mental health, the family environment is an important influence on only interpersonal relations, social support, and substance use.