Objective: Co-occurrence of substance use disorder and personality disorder (PD) is associated with greater functional impairment and mutual deterioration of the prognosis. More information is needed about the extent of personality problems in substance use disorder patients and when these problems can be assessed in a reliable way. The aim of this study was to compare the levels and scale reliability of (mal)adaptive personality functioning in four different samples and to discuss the possible clinical implications. Methods: Personality problems were assessed using the self-report Severity Indices of Personality Problems (SIPP) questionnaire in four samples: (a) 136 patients in the detoxification phase, (b) 187 patients with substance use disorder in long-term inpatient treatment, (c) 1,399 patients with PD in day and outpatient treatment, and (d) a community population of 935 respondents. Scale reliability of the SIPP facets was computed for each sample and levels of personality problems were compared among samples. Results: The scale reliability was acceptable for most of the SIPP facets in both substance use disorder samples. The substance use disorder samples had scores on SIPP that reflected greater personality dysfunction compared with the general community population and at a level similar to the PD population. Conclusions: SIPP appears to be a promising instrument for assessing personality pathology in substance use disorder treatment. The finding of high levels of maladaptive personality functioning in substance use disorder populations challenges the clinical management of the substance use disorder patient group and supports the development of integrated treatment approaches.
Keywords: Assessment; DSM-5; SIPP-118; personality disorder; personality problems; substance use disorder.