Third, “transitional” disorders with substantial loadings on two genetic factors provide further insights into the structure of the genetic risk for psychiatric disorders. Furthermore, the existence of these transitional disorders indicates that the psychiatric disorders in our current classification do not neatly fall into our four proposed clusters. Individuals with high criterion counts for borderline personality disorder were predicted by our results to require elevated genetic risk for both axis I and II externalizing disorders. Paranoid personality disorder stood out because it required risk genes from both the axis II internalizing and externalizing dimensions. Eating disorders had the most unusual configuration, requiring high risk on both the axis I internalizing and the axis II externalizing dimensions.
