This article was featured in the Cannabis Commerce + Chemistry Podcast No. 9. Listen now.
An August 2022 peer-reviewed research study entitled "Anhedonia, Apathy, Pleasure, and Effort-based Decision-making in Adult & Adolescent Cannabis Users & Controls" that was published in The International Journal of Neuropsychopharmacology explored the "lazy stoner" stereotype and whether cannabis consumption may lead to amotivation.
"Cannabis use has historically been linked with amotivation, which is reflected in prevalent, pejorative 'lazy stoner' stereotypes," reported the study. This scientific investigation demonstrated that "a relatively large group of adult and adolescent cannabis users and controls [who did not consume cannabis] did not differ on several measures of reward and motivation."
The study explained that cannabis is the "third most commonly used controlled substance worldwide, after alcohol and nicotine" (according to the United Nations Office on Drugs and Crime in 2020) and that the European Drug Report of 2020 noted that "19 percent of 15 to 24-year-olds reported past-year cannabis use, compared to 15 percent of 15 to 34-year-olds and eight percent of 15 to 64-year-olds."
"Cannabis use has historically been linked with amotivation, which is reflected in prevalent, pejorative 'lazy stoner' stereotypes," reported the study.
The study reported that 19 percent of 15-year-olds in England and 28 percent of 15- and 16-year-olds in the United States consumed cannabis within the past year. "Thus, cannabis use is disproportionately high among adolescents," concluded the study. "Adolescents may be particularly susceptible to effects of cannabis on mental health and cognition, including reward processing," noted the study's authors.
The study explained that reward processing "refers to any process that underpins the seeking and consumption of rewards and encompasses several reward sub-processes." It explained that, when reward processing becomes disrupted or skewed in humans, syndromes such as apathy (defined as a loss of or reduction in motivation) develop.
"Cannabis acts on the endocannabinoid system and repeated exposure may impair its sensitivity to rewarding stimuli and increase the susceptibility to...apathy in cannabis users," noted the study, which declared that its goal was to "assess multiple reward sub-processes simultaneously to gain a better understanding of the relationship between cannabis use and reward."
The research reported that it was "the first to directly compare adolescent and adult cannabis users in the same study."
The study's authors employed data from a previous 2020 "Cannteen" study involving 274 participants that included both adults (aged 26 to 29) and adolescents (16 and 17-years-old) who had consumed cannabis between one and seven days per week during the previous three month period. The research reported that it was "the first to directly compare adolescent and adult cannabis users in the same study."
The 2022 study found that previous investigations that analyzed "reward and motivation in cannabis users" suffered from small sample (cohort) sizes, making their results less reliable and valid. The study also found that, "despite the hypothesized adolescent vulnerability to harmful effects [from cannabis]," that "remarkably few studies" have compared adult cannabis consumers with adolescent cannabis users "directly on cognitive or psychological outcomes."
The 274 participants involved "76 adolescent cannabis users, 63 adolescent controls, 71 adult cannabis users, and 64 adult controls," all of whom were recruited from the Greater London area "via school assemblies, physical posters and flyers, and social media advertisements." The primary inclusion characteristic for participants in the four groups was "having used cannabis 1-7 days per week, on average, over the past three months."
The study excluded adult participant candidates "if they had used cannabis regularly prior to the age of 18" to isolate the impact of adolescent cannabis use. It declared other "key inclusion criteria" for control participants to be "having used cannabis or tobacco at least once but having less than 10 lifetime uses of cannabis and having no cannabis use in the month prior" to the study's data collection sessions.
The research reported that cannabis consumers who "used cannabis on average four days per week" did not display greater apathy.
"Importantly, adult and adolescent cannabis users were matched on frequency of use and days since last use," noted the study's authors.
The research reported that cannabis consumers who "used cannabis on average four days per week" did not display greater apathy or anhedonia [reduced motivation or ability to experience pleasure].
In fact, the researchers found that "cannabis users had significantly lower levels of anhedonia than controls" and that adolescents had "significantly higher levels of both anhedonia and apathy than adults." Despite this disparity, the study noted that "cannabis use did not augment this difference."
The study summarized that its initial hypothesis that "nonacute cannabis use is associated with reward processing impairments" was not supported by the data collected and that prior "large-scale studies in adolescent samples" found no association between cannabis use and apathy."
The researchers noted that "the relationship between cannabis...and apathy is likely to be complex and the interpretation of previous results is complicated by lack of ability to assess causality."
The study found "no association between cannabis use and apathy."
It concluded that its results, "together with previous evidence, suggest that adolescents are not at a greater vulnerability to cannabis-related apathy, disrupted effort-based decision-making, or blunted reward wanting or liking compared to adults." Like many other studies of cannabis use in humans, this one advised that more long-term research is necessary to confirm its findings.