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

• Published in: Neuropsychopharmacology (New York, N.Y.) N.Y.), 2019-07, Vol.44 (8), p.1456-1463
• Main Authors: Eikemo, Marie, Lobmaier, Philipp P, Pedersen, Mads L, Kunøe, Nikolaj, Matziorinis, Anna Maria, Leknes, Siri, Sarfi, Monica
• Format: Article
• Language: English
• Subjects: Addictions; Adult; Bayes Theorem; Bayesian analysis; Case-Control Studies; Choice Behavior; Computer applications; Decision Making; Diffusion models; Disruption; Drug abuse; Drug addiction; Drug use; Female; Hedonic response; Heroin; Humans; Models, Psychological; Narcotics; Opiate Substitution Treatment; Opioid-Related Disorders - drug therapy; Opioid-Related Disorders - psychology; Opioids; Reinforcement; Reward; Social interactions
• ISSN: 0893-133X; 1740-634X; 1740-634X
• DOI: 10.1038/s41386-019-0377-9

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 = 6.59, COMP = 6.67, p = 0.84, BF  = 0.29), yielding moderate evidence against subjective anhedonia in this OMT group. Importantly, the mothers in OMT also displayed robust reward responsiveness in the behavioral task (t  = 2.72, p = 0.013, BF  = 3.98; d = 0.61). Monetary reward changed their task behavior to the same extent as the local comparison group (reward bias OMT = 0.12, COMP = 0.12, p = 0.96, BF  = 0.18) 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.