A parallel process latent growth model of narcissistic personality disorder symptoms and normal personality traits

Although evidence from a number of longitudinal studies indicates a marked change in narcissistic personality disorder (NPD) symptoms over time, few studies have examined other psychological systems that may be related to this change. The current study uses data from the Longitudinal Study of Personality Disorders to examine how change in NPD symptoms is related to change in normal personality trait trajectories using parallel process growth curve modeling. A total of 250 students provided information on their personality traits and NPD symptoms on 3 occasions over the course of 4 years. Results suggest that cross-sectionally, NPD symptoms are positively correlated with dominance, neuroticism, and openness. Longitudinally, however, NPD symptoms decrease in parallel with increases in conscientiousness and decreases in neuroticism. Importantly, these longitudinal relationships are not a simple replication of the cross-sectional relationships between these 2 systems. Rather, this pattern of change is consistent with trait profiles suggesting maturation in young adults and has implications for the temporal stability of NPD as a construct and the theoretical relationship between normal personality traits and personality disorder more generally.