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Busting a stereotype. Marijuana will make you lazy and unmotivated, right? That’s the image that popular culture (and politicians) have cultivated for decades. Teens and young adults are especially potent targets for this message, with authority figures warning that marijuana use will sap their ambition and send them down a dead-end course for life. But new research published in the International Journal of Neuropsychopharmacology challenges the “lazy stoner” trope.
“We’re so used to seeing ‘lazy stoners’ on our screens that we don’t stop to ask whether they’re an accurate representation of cannabis users,” said Martine Skumlien, the study’s lead author and a PhD candidate at the University of Cambridge, in Neuroscience News. “Our work implies that this is in itself a lazy stereotype, and that people who use cannabis are no more likely to lack motivation or be lazier than people who don’t.”
Skumlien’s team consisted of researchers from University College London, King’s College London, and the University of Cambridge. They looked at the effects of cannabis use in both adults and teenagers, using study participants who said they used marijuana at least once per week over the previous three months. Average use among study participants was four days per week, with some participants saying they used marijuana every day. Participants in the control group were matched for age and gender.
The major takeaway: Cannabis users were no more likely than non-users to be apathetic or anhedonic (that is, to experience a loss of interest or pleasure). Nor were more frequent cannabis users likely to be more apathetic or anhedonic than their counterparts who partook less frequently.
The researchers came to this conclusion by first having participants answer questions about their emotions and interests (for instance, rating statements such as “I would enjoy being with family or close friends” or how interested they are in learning new things). Cannabis users scored similarly to non-users on measures of apathy and motivation, and scored lower than non-users on measures of anhedonia.
Around half of participants were also asked to complete some simple tasks, with a promise of small rewards (chocolates and other sweets) for completing these tasks. Participants could accept or reject the offers, and would get points toward rewards if the task was completed. Participants were also asked to rate who much they wanted several rewards—a £1 coin, a piece of candy, or listening to part of one of their favorite songs—and asked after receiving the reward how pleasurable they found it.
“We were surprised to see that there was really very little difference between cannabis users and non-users when it came to lack of motivation or lack of enjoyment, even among those who used cannabis every day,” said Skumlien. “This is contrary to the stereotypical portrayal we see on TV and in movies.”
This held true for adult and adolescent study participants—suggesting “that adolescents are no more vulnerable than adults to the harmful effects of cannabis on motivation, the experience of pleasure, or the brain’s response to reward,” study co-author Will Lawn told Neuroscience News. “In fact, it seems cannabis may have no link—or at most only weak associations—with these outcomes in general.”
“While adolescents had greater apathy and anhedonia than adults, cannabis use did not augment this difference; thus, adolescents were not more sensitive to the putatively damaging effect of cannabis,” the paper concludes.
The same team of researchers used the same participants in a study published earlier this year, this one using functional magnetic resonance imaging (fMRI) to look at brain activity during tasks measuring reward processing. This study also found no difference between cannabis users and non-users.
In both studies, the results held even for daily users.
Another co-author of the study, Barbara Sahakian of the University of Cambridge, noted to Neuroscience News that “we cannot rule out the possibility that greater use, as seen in some people with cannabis-use disorder, has an effect.” Longer-term studies will be necessary to determine how regular cannabis use affected motivation and developing brains over time.