Parameter estimates from the four genetic factors are presented in Table 3 and in Figure 1 (which includes all paths accounting for ≥10% of the genetic variance, that is, with loadings >0.316). Three broad patterns of findings are noteworthy. First, the four factors are all coherent and substantively interpretable. Factor 1 has strong loadings on four anxiety disorders (panic disorder, agoraphobia, specific phobia, and generalized anxiety disorder), major depression, eating disorders, and somatoform disorders. This factor reflects axis I internalizing disorders. Factor 2 is dominated by four personality disorders—schizoid, schizotypal, avoidant, and dependent—as well as dysthymia and social phobia. We name this factor axis II internalizing disorders, although it also contains two disorders traditionally placed on axis I. Factor 3 has strong loadings on four disorders reflecting antisocial behaviors (conduct disorder and antisocial personality disorder) and substance use disorders (alcohol and drug abuse or dependence). This factor identifies an axis I externalizing disorders dimension although it includes one category (antisocial personality disorder) that is traditionally placed on axis II. Factor 4 contains the five remaining personality disorders—histrionic, narcissistic, obsessive-compulsive, borderline, and paranoid—and is best interpreted as an axis II externalizing disorders dimension.
