Does change in temperament predict change in schizoid personality disorder? A methodological framework and illustration from the Longitudinal Study of Personality Disorders.

Personality disorders (PDs) have been thought historically to be enduring, inflexible, and set in psychological stone relatively firmly; however, empirical findings from recent prospective multiwave longitudinal studies establish otherwise. Nearly all modern longitudinal studies of personality disorder have documented considerable change in PDs over time, suggesting considerable flexibility and plasticity in this realm of psychopathology. The factors and mechanisms of change in the PDs remain essentially opaque, and this area of PD research is just beginning to be probed using candidate predictors of change, such as personality systems. In this report, we investigate whether change in temperament dimensions (emotionality, activity, and sociability) predicts change in schizoid personality disorder. We present a latent growth framework for addressing this question and provide an illustration of the approach using data from the Longitudinal Study of Personality Disorders. Schizoid personality disorder was assessed using two different methodologies (structured psychiatric interview and self-report) and temperament was assessed using a well-known psychometric measure of temperament. All constructs were measured at three time points over a 4-year time period. To analyze these panel data, we fitted a covariance structure model that hypothesized simultaneous relationships between initial levels and rates of change in temperament and initial levels and rates of change in schizoid personality disorder. We found that rates of change in the core temperament dimensions studied do not predict rates of change in schizoid personality over time. We discuss the methodological advantages of the latent growth approach and the substantive meaning of the findings for change in schizoid personality disorder.