Financial incentives for substance abstinence: a systematic review and meta-analysis.

Introduction: Substance Use Disorder (SUD) increased by 45% globally in the past 10 years, representing one of the largest increases in risk factors for disease. Financial incentives (FI) are a promising tool to promote health behavior change, including substance abstinence. We aim to address a 10-year gap in the evidence and identify key characteristics for optimal treatment.

Methods: A meta-analysis of randomized controlled trials (RCTs) was undertaken per Cochrane guidelines and the PRISMA 2020 checklist. Medline, PsycINFO, and EMBASE were searched up to 11th September 2024. Included studies offered FI to substance users in exchange for substance abstinence compared to an alternative intervention control. The primary outcome extracted was substance abstinence at latest follow-up. Secondary outcomes such as cost-effectiveness, adverse events, and motivational assessments were also extracted. Risk of bias was analyzed using the RoB 1 tool.

Results: Of 5,042 studies identified, 246 were shortlisted for full-text review and included 39 RCTs (N = 27,845) for meta-analysis. SUD categories spanning nicotine (n = 30, OR = 1.83; 95%CI = 1.65-2.03, p < .001), alcohol (n = 3, OR = 4.69, 95%CI = 1.59-13.86, p = .005), stimulants (n = 2, OR = 3.52; 95%CI = 0.36-34.18, p = 0.28), and polydrug (n = 2, OR = 3.11, 95%CI = 0.53-18.25, p = 0.21) were meta-analyzed for improving abstinence rates. Cannabis and opioid sub-groups could not be meta-analyzed. Overall effectiveness was significant for FI improving substance abstinence rates (OR=1.93, 95%CI=1.66-2.24, p<.001) with continued significance through 12-month or longer follow-ups (OR=1.78; 95%CI=1.50-2.12, p<.001).

Conclusions: Findings from this meta-analysis suggest that FI are an effective tool for increasing substance abstinence, particularly nicotine and alcohol, however, future research is recommended for other substances such as stimulants and opioids.

Implications: This systematic review and meta-analysis exploring the use of financial incentives for substance use disorders provides the first update on trends in this field since 2014 and the first meta-analysis since 2006. Notably, this review challenges the concerns of sustainability and effects on motivation which have withheld the clinical application of financial incentives for substance use disorders.