Substance-free and substance-related reinforcement in relation to substance use: A meta-analysis

Contemporary behavioral economic theory conceptualizes addiction as an operant reinforcer pathology in which substance use is substantively influenced by reinforcement obtained through substance-free sources. The aim of the current meta-analysis was to quantitatively synthesize cross-sectional associations between both substance-related and substance-free reinforcement in relation to substance use and substance-related problems.

Systematic bibliographic searches were conducted in PubMed and PsychINFO from 1998 to 20 March 2026. Main eligibility criteria included human, peer-reviewed studies that measured substance use, the reinforcement ratio (proportionate substance-related reinforcement), substance-related reinforcement and/or substance-free reinforcement, which yielded 28 studies and 31 samples. Pearson's r correlations were extracted for the reinforcement ratio, substance-related reinforcement and substance-free reinforcement in relation to substance use problem/severity and quantity/frequency outcomes. Six random effects meta-analyses were conducted based on these key variables, with an average aggregated sample size of n = 5663 (range = 4344-7258).

The reinforcement ratio (RR) and substance-related reinforcement (SR) were statistically significantly associated with both substance use problem/severity [RR r = 0.33, 95% confidence interval (CI) = 0.27-0.39, number of effect estimates (k) = 19, I² = 85.06, SR r = 0.34, 95% CI = 0.29-0.60, k = 12, I² = 94.28, Ps < 0.001] and quantity/frequency (RR r = 0.38, 95% CI = 0.31-0.46, k = 17, I² = 86.22, SR r = 0.34, 95% CI = 0.25-0.43, k = 10, I² = 87.99, Ps < 0.001). Substance-free reinforcement was statistically significantly negatively associated with quantity/frequency (r = -0.11, 95% CI = -0.17 to -0.04, k = 13, I² = 81.57, P = 0.002) but not problem/severity of substance use (r = -0.07, 95% CI = -0.14 to 0.00, k = 16, I² = 83.38, P = 0.051). Continuous study moderators (% male, % White, study year) and categorical study moderators (reinforcement measurement tool) explained some heterogeneity across analyses. Overall, there was minimal evidence of publication bias.

Substance-related reinforcement and the reinforcement ratio appear to be moderately strong correlates of substance problems/severity and quantity/frequency outcomes.