Cannabis Use Itself May Not Lead to Apathy

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The public, as well as many elected officials, continue to believe that the regular use of cannabis leads to amotivation and diminished effortful behavior. However, whether the amotivational syndrome exists or not is still controversial; there are still too few studies on the topic, and those that exist are often poorly controlled and small. They do not allow a definitive answer.

Is Cannabis Use Linked to Amotivation?

Moreover, most of these earlier studies largely failed to consider the potentially confounding influences of preexisting depression, the abuse of other substances, such as nicotine, and personality disorders—despite known relationships between these variables and cannabis use. Also, most people who use marijuana do not show typical symptoms, such as apathy, dullness, lethargy, and impairment of judgment.

Some recent, well-controlled studies have investigated whether amotivational syndrome exists, and if so, what factors underlie increased vulnerability for some users.

The amotivation syndrome hypothesis suggests that regular cannabis use (the term regular is often the source of some contradictory findings) results in impaired capacity for goal-directed behavior. A recent study of college students examined the relationship between cannabis use and effort-related decision-making (Acuff SF et al., 2023).

Recent Studies Suggest Cannabis Use May Not Be Linked to Amotivation

The majority of cannabis users in this study met the criteria for cannabis use disorder. The study controlled for attention-deficit/hyperactivity disorder (ADHD) symptoms, distress tolerance, and income. The results indicate that college students who use cannabis are more likely to expend extra effort to obtain rewards. This was true even after controlling for the magnitude of the reward and the probability of obtaining the reward. Overall, the results of this study do not support the amotivational syndrome hypothesis.

Another recent study examined the use of cannabis on motivated behavior and self-reported apathy. Regular cannabis users (about three days/week during the past year) were compared to controls (who reported using cannabis only once per month during the previous year), who completed the Apathy Evaluation Scale and the Effort Expenditure for Rewards Task. The researchers controlled for alcohol use and the presence of depression since both are linked to cannabis use.

Cannabis Users May Be More Motivated Than Non-Users

The study discovered that as the magnitude of the reward and the probability of winning the reward increased, cannabis users were significantly more likely to select harder tasks to complete. In contrast to the amotivational hypothesis, cannabis users were more likely to exert greater effort for reward, demonstrating enhanced motivation relative to controls.

A third recent investigation tested whether prolonged cannabis use has residual effects on motivation.

This study also utilized performance on the Effort Expenditure for Reward Task on a group of cannabis users and non-users. This study also reported that cannabis users selected hard trials significantly more than non-users.

Overall, the results of these recent investigations do not support the development of amotivational syndrome in young adults who are frequent cannabis users. Cannabis use at a frequency of three to four days per week was not associated with apathy, effort-based decision-making for reward, reward-wanting, or reward-liking in adults or adolescents.

However, some individuals, due to the presence of undiagnosed psychiatric disorders, may be vulnerable to even occasional cannabis use and may develop symptoms typically associated with the amotivational disorder.