Fifth, of the five phobias we examined, only AgP loaded substantially on the internalizing genetic common factor. Consistent with prior studies that suggest that the internalizing spectrum may contain a second partially independent ‘fear-based’ factor (Krueger, 1999; Vollebergh et al. 2001), we found that SoP, SiP, BiP and AnP made only very modest contributions to the overall internalizing genetic common factor. However, our results for PD, at least in females, were not fully consistent with this hypothesis.
