Predictive validity of the PCL-R for offenders with intellectual disability in a high security hospital: Treatment progress

Background Among mainstream offenders, the severe personality disorder of psychopathy has considerable importance as a construct. The disorder has long been associated with failure to make treatment progress. Previous work has identified that psychopathy as a disorder occurs in samples of offenders with intellectual disability ( ID), and suggests that the Psychopathy Checklist - Revised ( PCL- R: Hare, 1991, 2003) as a measure of the disorder has adequate reliability and validity ( Morrissey et al., 2005). The present study aimed to compare the predictive power of the PCL- R in relation to treatment progress with a more general assessment of violence risk, the HCR- 20 ( Webster, Douglas, Eaves, & Hart, 1997). Method A sample of 73 residents in a high security intellectual disability service, who had previously been assessed using the PCL- R and the HCR- 20, were followed up at 2 years post- assessment, and their outcome determined in terms of two distinct dichotomous variables reflecting definite positive treatment progress and definite negative treatment progress respectively. Results In line with predictions, the PCL- R Total score and Factor 1 score ( Interpersonal and Affective aspects of psychopathy) and the HCR- 20 Total score were significantly inversely associated with a positive move from high to medium security hospital conditions within 2 years of assessment. However against prediction, the PCL- R Total score had incremental validity over the HCR- 20. The PCL- R Total and Factor 1, but not the HCR- 20 Total score, were also significantly associated with negative treatment progress in terms of a move to more restricted treatment conditions. Conclusion Psychopathy, and in particular its interpersonal and affective manifestations, is a construct which appears to be associated with indirect measures of treatment progress in this high security ID group. However, caution should be applied in the use of a construct with potentially negative connotations in an already devalued population.