Daily Cannabis Users Show Normal Brain Value Signals for Cannabis But Disrupted Signals for Non-Drug Rewards

Subjective value signals for cannabis appeared in vmPFC, ventral striatum, and dorsal PCC as expected. Value encoding in vmPFC was stronger for cannabis than snacks. For snack rewards, expected value signals were absent. Cannabis and snack cues differentially modulated value encoding in the dorsal PCC. Choice behavior was equivalent between reward types despite the neural differences.

Inpatient crossover design with 21 non-treatment-seeking near-daily cannabis users (20 analyzed). Four conditions crossing cue type (neutral/drug or neutral/snack) with reward type (cannabis/snack). fMRI during economic choice task choosing between 0-6 cannabis puffs or snacks vs. fixed monetary amounts.

This study provides neural evidence for a key addiction theory: that problematic substance use involves not just enhanced drug valuation but degraded valuation of non-drug rewards. The behavioral equivalence masking neural differences suggests standard behavioral measures may miss this dysfunction.

The dissociation between intact cannabis value signals and disrupted food value signals supports theories that addiction involves a narrowing of reward valuation rather than simple overvaluation of the drug. This has implications for treatment targets.

Small sample (n=20). Only 1 female participant. Non-treatment-seeking users. Cross-sectional design cannot determine if neural differences preceded cannabis use. Snacks may not adequately represent all non-drug rewards.