A psychometric evaluation of the Defense Style Questionnaire in methadone patients.

The self-report Defense Style Questionnaire (DSQ) was designed to assess defenses along a developmental continuum. Factor analysis of the original DSQ suggested that the scale assessed four factors or types of defenses, whereas a more recent factor analysis indicated the DSQ measured three-factors: Immature, Neurotic, and Mature. No data, however, regarding the reliability or unique construct validity of DSQ dimensions was published. This article reports on factor analyses of two DSQ versions in a sample of 215 methadone maintenance patients. Results indicate that both DSQ versions are unidimensional, assessing only Immature defenses. The lack of published psychometric data raises concerns regarding the true reliability of DSQ dimensions reported in previous investigations. Prior statements based on DSQ findings may have been incorrect if the DSQ factors were unreliable. Findings from this investigation stress the importance of requiring and evaluating the psychometric integrity of an instrument before employing it in research.