Effects of methamphetamine on human effort task performance are unrelated to its subjective effects

Psychopharmacology (Berl). 2025 Jul 8. doi: 10.1007/s00213-025-06853-4. Online ahead of print.

ABSTRACT

RATIONALE: Stimulant drugs increase objective indices of reward-related behavior, including willingness to expend effort for reward, and also produce feelings of well-being and positive mood. However, it is not known to what extent these different measures are related to each other.

OBJECTIVES: The present study was designed to assess the relationship between the behavioral measure of effort expenditure and positive subjective responses to methamphetamine (MA).

METHODS: 96 healthy adults completed the Effort Expenditure for Rewards Task (EEfRT) during two laboratory sessions after receiving 20 mg MA or placebo (PL) under double blind conditions. They also self-reported their mood states and drug effects.

RESULTS: MA (vs. PL) increased willingness to complete a high effort/high reward option vs. a low effort/low reward option during the EEfRT (N = 96), and this effect was greater in participants with low effort at baseline. A subjective value modeling analysis (N = 91) showed that MA decreased sensitivity to the perceived cost of effort for the low baseline performance group only. MA also increased self-reported positive affect (euphoria; N = 94, liking the drug; N = 92) in the full sample, but this increase was unrelated to either baseline EEfRT performance or MA-induced EEfRT performance changes (N = 91).

CONCLUSIONS: As reported previously, MA increased choice of the high effort/high reward option, particularly in participants with low effort at baseline, who also showed drug-induced changes in effort sensitivity. These behavioral effects were not related to drug liking and drug-induced euphoria. These findings suggest that the effects of stimulants on reward-related behavior and mood are dissociable.

PMID:40627130 | DOI:10.1007/s00213-025-06853-4