Substance abuse is associated with criminal recidivism. Substance abuse treatment has been found to correlate negatively with re-offending among treatment utilizers. However, for offenders with mental health problems and substance abuse, research on how substance abuse treatment affects re-offending is sparse.

The study aimed to examine the relationship between self-reported outpatient-based substance abuse treatment and self-reported a) re-offending, b) substance use and c) psychiatric problems among offenders with mental health and substance use problems.

Data were gathered from a naturalistic follow-up study with 208 participants, subjected to a court-ordered psychiatric assessment. This analysis covers 91 individuals who were followed-up after an average study period of 17 months. Among these, 68% had been sentenced to institutional imprisonment or forensic psychiatric care.

Offences, substance use and psychiatric problems declined between baseline and follow-up. However, the reduction was not associated with self-reported treatment utilization. Among participants who were sentenced to non-institutional corrections, more individuals had utilized outpatient-based treatment compared to individuals who were sentenced to imprisonment or forensic psychiatric care.

A definitive conclusion about the effect of treatment is difficult to draw. For instance, self-reported data may not reflect actual treatment consumption. However, one interpretation is that participants naturally recovered over time. Institutional correction might also have resulted in positive outcomes equivalent to outpatient-based treatment.