The critical growth parameter for investigating stability and changein PD features over time is the individual slope parameter, as it directlyindexes the rate and direction of individual change over time. In the level2 prediction of slope, group membership was significantly predictive of therate of change in PD features for total PD features; cluster A, B, and C dimensions;and the paranoid, borderline, narcissistic, histrionic, avoidant, obsessive-compulsive,and dependent PDs (all P≤.05). For these PD dimensions,the median effect size was 0.26, indicating a medium-sized effect, and thedirection of the fixed effects shows that PPD subjects were showing higherrates of change (ie, PD feature declines). Group status was less predictiveof rate of change for schizoid (P < .43),schizotypal (P < .06), passive-aggressive(P < .24), and antisocial (P < .10) PDs. Inspection of the fixed effects for sexindicate that it was less predictive of slope and, therefore, essentiallyunrelated to change in PD features over time, attaining statistical significanceonly for narcissistic PD (P < .03).Overall, the effect sizes for sex in relation to the rate of change were quitesmall (median effect size, r = 0.07). Ageat entry into the LSPD was minimally associated with the rate-of-change parameters(Table 4). Overall, study group statuswas the factor most strongly associated at level 2 with rate of change inthe PDs. For many PD dimensions, namely clusters A and B and schizoid, schizotypal,antisocial, borderline, narcissistic, and histrionic PD, the variance componentestimates for rate of change (σ21) indicated therewas also additional significant variation in elevation that could still bemodeled beyond the 3 predictors that we had selected.