Exploratory factor analysis of the specific environmental correlation matrix revealed six factors with eigenvalues exceeding unity: 5.17, 2.70, 1.46, 1.34, 1.19, and 1.10. Examining the scree plot suggests a break between three and four factors. Adding a third factor identified a coherent bipolar factor with salient loadings on five disorders (environmental factor 3 below). Adding a fourth factor, by contrast, identified a minimally coherent factor with loadings on only two disorders—positive on drug abuse or dependence and negative on dependent personality disorder. We again saw this as evidence of overextraction, so we present results from a four-factor genetic and a three-factor unique environmental solution.
