A Latent Class Analysis of Mental Disorders, Substance Use, and Aggressive Antisocial Behaviour Among Swedish Forensic Psychiatric Patients ^†

Abstract

Patients in forensic mental health services (FMHS) with co-occurring mental disorders (MD), substance use disorders (SUD), and a history of violent crime—often referred to as the “triply troubled”—represent one of the most clinically complex and poorly researched patient populations. Standard diagnostics tend to treat this group as homogeneous, which may impede the development of patient-centred treatment and risk management. This study aimed to identify patient subgroups within this population based on patterns of MDs, substance use history, and aggressive antisocial behaviour (AAB). A latent class analysis (LCA) was conducted using clinical data from 119 patients at a high-security FMHS facility in Sweden. Indicator variables included lifetime diagnoses of SUD and MDs and types of substances used. History of AAB and criminal offending were used as distal outcomes. A four-class solution provided the best model fit. Class 1 (polysubstance, high AAB; 100% SUD probability) and Class 4 (polysubstance, bipolar disorder; 49% SUD probability) exhibited pronounced criminal and AAB history. Class 2 (psychosis and cannabis-limited substance use) and Class 3 (autism and limited substance use) represented less criminologically ladened subgroups. Notably, Classes 1 and 4 shared extensive AAB histories despite differing SUD diagnostic probabilities, highlighting the limitations of diagnosis alone as a basis for risk assessment. The four-class typology offers a clinically meaningful framework for stratifying triply troubled patients in FMHS, aligning with the Risk–Need–Responsivity model and severity-graded treatment recommendations The typology has direct implications for treatment differentiation, relapse prevention, and risk management in forensic psychiatric settings.