Effort-Based Decision Making and Self-Reported Apathy in Frequent Cannabis Users and Healthy Controls

Abstract

Background: Cannabis use rates have been escalating in recent years within the United States, and the effects of cannabis on motivation and effort-based decision making have been of increased interest. Amotivational syndrome is a term used to refer to lack of motivation, passive personality, non-productive behavior, and lower educational attainment related to chronic cannabis use. However, past literature has reported mixed findings for the effects of cannabis on motivation across both behavioral and self-report studies; therefore, the current study aimed to evaluate the association between frequent cannabis use, motivated behavior, and self-reported apathy in individuals 18 years and older. Methods: Cannabis users who reported, on average, 3 or more days/week of cannabis use over the past year, and healthy controls who reported once/month or less cannabis use over the past year were recruited. Participants withheld from substance use 12 hours prior to the study visit. They completed a breathalyzer test, urine toxicology screen, the Apathy Evaluation Scale (AES), and the Effort Expenditure for Rewards Task (EEfRT), a computerized button-pressing task that measures effort-based decision making whereby individuals must increase effort for monetary reward. There were no significant differences between groups on any demographic characteristics except for past 30-day alcohol use (p = 0.001), and depression scores (p = 0.005; determined by the Beck Depression Inventory-II), which were both greater in cannabis users relative to healthy controls. A repeated measures analysis of covariance (ANCOVA) was used to examine the effects of Group, reward magnitude, probability, and their interaction on hard task selections on the EEfRT, controlling for alcohol and depressive symptoms. A separate ANCOVA examined between-group differences on the AES with the same covariates. Results: The main results indicated that relative to healthy controls, cannabis users were significantly more likely to select hard tasks on the EEfRT regardless of reward magnitude or probability of winning the reward (p = 0.014, partial η2=0.10). Self-reported apathy was higher in cannabis users relative to controls (p = 0.02), but after controlling for alcohol use and depressive symptoms, these group differences were no longer significant (p = 0.46). Furthermore, the number of hard task selections on the EEfRT was not significantly related to self-reported apathy in cannabis users (p = 0.68), or healthy controls (p = 0.52). Conclusions: These findings indicate that cannabis users exhibit a greater likelihood of exerting more effort for reward, suggesting enhanced motivation relative to healthy controls. Thus, the current results do not support the amotivation hypothesis in adult frequent cannabis users. Despite some harms of frequent cannabis use, amotivation may not be among them.