Several caveats should be mentioned in considering these LSPD data. Compared with the US population at large, the LSPD sample is more homogeneous in age, educational achievement, and social class, which may differentially affect the study results. Also, the LSPD was begun when the subjects were first-year university students and some of the most severely affected individuals with PD might have never successfully enrolled in college and therefore would not be included in the study. However, one must recall the Axis I diagnostic data for the LSPD subjects (Table 2), diagnosed according to rigorous clinical thresholds, before ascribing undue levels of mental health to these subjects. Multiwave longitudinal data from clinically based PD samples, mindful of their limitations for generalization, are needed for contrast with the LSPD results. Finally, one could argue that the stability observed for PD features in this study might be artifactual (ie, subjects portray themselves as more consistent than they really are); however, a large methodological literature in the personality assessment domain has rendered such an assertion untenable.1 The present data will be further dissected using additional approaches to the analysis of stability, including analysis of latent growth curves and factorial invariance, as well as structural equation–based approaches to the analysis of stability and change.8,10,11,21 William James33(p121) claimed that "by the age thirty, the character has set like plaster, and will never soften again," and that indeed seems to be true of normal personality.1 However, clinical experience suggests that some PD features may diminish with age. Continued lifespan study of the LSPD subjects will offer the opportunity to determine if James' view also holds for PD. Finally, this study is best viewed as heuristic and hypothesis-generating, undertaken within a context of exploration rather than a context of justification or confirmation.