A psychometric evaluation of the Defence Style Questionnaire-40 in a UK forensic patient population

Psychological defence mechanisms have been considered important personality processes in the onset, maintenance and recovery of mental disorders. More recently, their application to understanding presenting problems and as potential outcome indicators for forensic patients has been recommended. However, to date there have been no investigations into the reliability and factor structure of defence mechanism assessments for this population. The current study investigated the factor structure, internal consistency and test-retest reliability of the Defence Style Questionnaire-40 (DSQ) for 160 adult male UK forensic patients. The three-factor model of defences proposed by the DSQ-40 developers was not confirmed in the study sample. Reliability indices of the three factors indicated that the Immature factor was the most ‘acceptable’ in terms of internal consistency. Test-retest reliability coefficients ranged from .70 to .91. A revised three-factor structure that closely corresponds to the original validation study is recommended following an exploratory factor analysis. The findings are compared with previous reliability and factor analytic evaluations of the DSQ-40, and recommendations for its use with forensic patients are discussed.