Outcome measures in forensic mental health services: A systematic review of instruments and qualitative evidence synthesis

Background Outcome measurement in forensic mental health services can support service improvement, research, and patient progress evaluation. This systematic review aims to identify instruments available for use as outcome measures in this field and assess the evidence for the most common instruments, specific to the forensic context, which cover multiple outcome domains. Methods Studies were identified by searching seven online databases. Additional searches were then performed for 10 selected instruments to identify additional information on their psychometric properties. Instrument manuals and gray literature was reviewed for information about instrument development and content validity. The quality of evidence for psychometric properties was summarized for each instrument based on the COnsensus-based Standards for health Measurement INstruments (COSMIN) approach. Results A total of 435 different instruments or variants were identified. Psychometric information on the 10 selected instruments was extracted from 103 studies. All 10 instruments had a clinician reported component with only two having patient reported scales. Half of the instruments were primarily focused on risk. No instrument demonstrated adequate psychometric properties in all eight COSMIN categories assessed. Only one instrument, the Camberwell Assessment of Need: Forensic Version, had adequate evidence for its development and content validity. The most evidence was for construct validity, while none was identified for construct stability between groups. Conclusions Despite the large number of instruments potentially available, evidence for their use as outcome measures in forensic mental health services is limited. Future research and instrument development should involve patients and carers to ensure adequate content validity