Substance use disorder (SUD) is a major global health challenge, causing significant individual suffering and a high burden on health systems and society. Music therapy (MT) has emerged as a promising supplementary intervention, as music engages the brain's reward system in ways analogous to addictive substances while fostering positive reinforcement, stress reduction, and emotional regulation. Given high relapse rates in the first year post-treatment, identifying appropriate outcome measurement instruments for the long-term evaluation of MT is of critical importance. This report was conducted within the framework of the European Horizon Europe project FALCO (Fighting Addictions, improving Lives: COmprehensive drug rehabilitation with music), involving seven countries.

A systematic literature search was conducted in February 2025 across four databases (The Cochrane Library, Embase, HTA-INAHTA, MEDLINE). Following the screening of 451 citations, seven systematic reviews were included. Based on predefined selection criteria – including frequency of use, validated and reliable psychometric properties, as well as coverage of all identified outcome parameters – 14 measuring instruments were selected for detailed characterisation. A complementary manual search identified 13 additional instruments capturing socioeconomic outcomes. Nine semi-structured interviews with service users from Austria, Norway and Poland were analysed using qualitative content analysis to incorporate patient-relevant perspectives.
Seven included reviews yielded more than 60 outcomes across 11 parameters, including substance use, recovery, craving, motivation, quality of life, mood, and social and socioeconomic parameters. No tools for assessing (serious) adverse events were identified. A Minimal Clinically Important Difference (MCID) was established only for depression, and not specifically for SUD populations. Instruments measuring stable constructs – such as depression, problem severity, and self-efficacy – were identified as being most appropriate for long-term measurement. Key limitations included self-report bias, challenges with cultural adaptation, and training requirements for clinician-administered tools. Service user interviews revealed that social parameters were by far the most frequently mentioned aspect of recovery. Latent content analysis identified four recurring narrative patterns around social exclusion, cycles of use and recovery; with children, pets, and employment emerging as key facilitators of social reintegration.

Validated outcome instruments for MT in SUD exist, but critical gaps remain: absent SUD-specific MCIDs, limited long-term evidence, no adverse event protocols, and systematic underrepresentation of social recovery. Future research should prioritise long-term follow-up studies, consensus-based core outcome sets, and culturally adapted instruments that incorporate social and socioeconomic dimensions. A participatory mixed-methods design is recommended, with service user perspectives integrated from the outset in the selection of instruments and study designs.