Psychiatry · Medical Literature
Cost-effectiveness of a mentalisation-based treatment for antisocial personality disorder in males convicted of an offence on community probation in England and Wales: Multicentre, assessor-blind randomised controlled trial.
Abstract
This study addresses a critical gap in the evidence base for cost-effective psychological interventions for antisocial personality disorder (ASPD) in forensic settings by presenting a full trial-based economic evaluation of mentalisation-based treatment plus probation as usual (MBT-ASPD + PAU), compared to PAU alone, for males with ASPD convicted of an offence in England and Wales. The economic evaluation adopted a societal perspective, incorporating costs to health care, the criminal justice system, and the wider societal impact of offending. Outcomes were assessed 24 months post-randomisation. The primary cost-utility analysis compared costs with quality-adjusted life years (QALYs) derived from the EQ-5D-5L, while a secondary cost-effectiveness analysis compared costs with aggression outcomes measured by the Overt Aggression Scale - Modified (OAS-M). Although missing data limited definitive conclusions regarding service use, available data suggest that participants in the PAU group spent more time in custody than those in the MBT-ASPD + PAU group. Utility scores and quality of life showed minimal variation over follow-up, with no significant differences between groups. Overall costs were lower in the MBT-ASPD + PAU group, though not statistically significant. Over the 24-month period, MBT-ASPD + PAU was associated with both reduced costs and lower aggression (as reflected in OAS-M scores), indicating that each unit reduction in aggression yielded a cost saving of approximately £93. For QALYs, MBT-ASPD + PAU appeared cost-effective compared to PAU across all values a decision-maker may be willing to pay for improvements in outcome. These findings provide preliminary evidence for the potential economic value of MBT-ASPD + PAU in a forensic ASPD population, particularly in relation to aggression reduction and the associated cost savings. Trial registrationThis trial is registered with ISRCTN (ISRCTN 32309003).
Clinical relevance
Antisocial personality disorder (ASPD) in forensic populations represents a high-burden, historically treatment-resistant condition with substantial costs to healthcare, the criminal justice system, and society, yet robust economic evidence for psychological interventions in this group has been virtually absent. This multicentre RCT addresses that gap by providing the first full trial-based economic evaluation of mentalisation-based treatment adapted for ASPD (MBT-ASPD) in males on community probation in England and Wales. The findings are timely given increasing policy focus on diverting offenders with personality disorder away from custody and toward evidence-based community interventions.
Key findings
1. MBT-ASPD plus probation as usual (MBT-ASPD + PAU) was associated with lower overall societal costs compared to PAU alone over 24 months post-randomisation, though this difference did not reach statistical significance, limiting definitive conclusions. 2. Participants in the PAU-alone group spent more time in custody than those receiving MBT-ASPD + PAU, suggesting a potential criminal justice cost offset attributable to the intervention, though missing service-use data constrain interpretation. 3. In the secondary cost-effectiveness analysis using the Overt Aggression Scale – Modified (OAS-M), each unit reduction in aggression in the MBT-ASPD + PAU group was associated with an estimated cost saving of approximately £93, indicating a dominant economic profile on this outcome. 4. In the primary cost-utility analysis using QALYs derived from the EQ-5D-5L, MBT-ASPD + PAU appeared cost-effective compared to PAU across the full range of willingness-to-pay thresholds a decision-maker might apply, suggesting probabilistic dominance or acceptability across conventional thresholds. 5. Utility scores and health-related quality of life showed minimal variation over the 24-month follow-up period, with no statistically significant between-group differences on QALYs, reflecting the well-documented insensitivity of generic preference-based measures in forensic personality disorder populations. 6. The economic evaluation adopted a broad societal perspective incorporating healthcare costs, criminal justice system costs, and wider societal impact of offending, making the findings more generalisable to policy-level decision-making than analyses limited to healthcare costs alone.
Practice implications
Clinicians and commissioners working with males with ASPD on community probation should consider MBT-ASPD as a potentially cost-effective adjunct to standard probation supervision, particularly given its association with aggression reduction and lower time in custody, outcomes that matter both clinically and economically. Patient selection should prioritise males with confirmed ASPD in forensic community settings, consistent with the trial population, and services should be prepared to address high rates of missing data through robust engagement and retention strategies, as data completeness was a key limitation affecting definitive conclusions. These preliminary findings justify investment in larger, adequately powered replication studies with enhanced data collection protocols before MBT-ASPD is adopted as standard of care, but they provide sufficient economic signal to support pilot implementation within existing probation-linked personality disorder pathways in England and Wales.