Intact responses to non-drug rewards in long-term opioid maintenance treatment

Abstract

Disruption of non-drug reward processing in addiction could stem from long-term drug use, addiction-related psychosocial stress, or a combination of these. It remains unclear whether long-term opioid maintenance treatment (OMT) disrupts reward processing. Here, we measured subjective and objective reward responsiveness in 26 previously heroin-addicted mothers in >7 years stable OMT with minimal psychosocial stress and illicit drug use. The comparison group was 30 healthy age-matched mothers (COMP). Objective reward responsiveness was assessed in a two-alternative forced-choice task with skewed rewards. Results were also compared to performance from an additional 968 healthy volunteers (meta-analytic approach). We further compared subprocesses of reward-based decisions across groups using computational modelling with a Bayesian drift diffusion model of decision making. Self-reported responsiveness to non-drug rewards was high for both groups (means: OMT\u2009=\u20096.59, COMP\u2009=\u20096.67, p\u2009=\u20090.84, BF10\u2009=\u20090.29), yielding moderate evidence against subjective anhedonia in this OMT group. Importantly, the mothers in OMT also displayed robust reward responsiveness in the behavioral task (t19\u2009=\u20092.72, p\u2009=\u20090.013, BF10\u2009=\u20093.98; d\u2009=\u20090.61). Monetary reward changed their task behavior to the same extent as the local comparison group (reward bias OMT\u2009=\u20090.12, COMP\u2009=\u20090.12, p\u2009=\u20090.96, BF10\u2009=\u20090.18) and in line with data from 968 healthy controls previously tested. Computational modelling revealed that long-term OMT did not even change decision subprocesses underpinning reward behavior. We conclude that reduced sensitivity to rewards and anhedonia are not necessary consequences of prolonged opioid use.