Figure.

Parameter estimates for genetic and environmental factors from the best-fit multivariate twin model applied to the 9 DSM-IV criteria for major depression. A, Parameter estimates for genetic factors from the best-fit multivariate twin model applied to the 9 DSM-IV criteria for major depression. Three genetic common factors were identified as well as genetic factors unique to each criterion. Factor loadings from the common factors of 0.31 or more are bold. A1 through A3 refer to the first through third common genetic factors. A₁ through A₉ refer to the criteria-specific genetic influences for criteria 1 through 9, respectively. Squares are observed variables and circles/ovals indicate latent variables. B, Parameter estimates for environmental factors from the best-fit multivariate twin model applied to the 9 DSM-IV criteria for major depression. One common and 3 individual-specific environmental common factors were identified as well as individual-specific environmental factors unique to each criterion. Factor loadings from the common factors of 0.31 or more are bold. C1 and E1 through E3 refer, respectively, to the single common shared environmental and the first through third common individual-specific environmental factors. E₁ through E₉ refer to the criteria-specific individual-specific environmental influences for criteria 1 through 9, respectively. Squares are observed variables and circles/ovals indicate latent variables.