The structural core of dual diagnosis: Personality structure profiles in substance use disorders with and without Comorbid personality pathology

The coexistence of substance use disorders (SUDs) and personality disorders (PDs) is a complex and frequent phenomenon that presents significant clinical challenges. This study adopted Kernberg's Object Relations Theory (ORT) to explore differences in profiles of personality structure among SUD patients with and without comorbid PD. A total of 60 nonclinical participants, 45 outpatients with SUDs, and 42 inpatients with both SUD and PD (dual diagnosis, DD) were assessed using the STIPO-R, a semi-structured interview grounded in ORT. Group differences were analyzed across all domains and subdomains of the interview. The STIPO-R effectively distinguished both DD and SUD patients from nonclinical participants across all domains and subdomains of personality functioning. However, after adjusting for age and gender, no significant differences emerged between DD and SUD groups. Both clinical groups showed comparable levels of impairment across identity, object relations, defenses, aggression, moral functioning, and narcissism. Our findings support the utility of the STIPO-R and highlight the relevance of dimensional models in capturing personality dysfunction in SUD populations, even in the absence of comorbid PD.