Increasing efforts around the world to legalize cannabis for recreational purposes have led to growing concern about how this trend affects adolescent mental health. Clinical neuropsychologist Krista Lisdahl of the University of Wisconsin-Milwaukee has been studying cannabis use in this population for two decades and expresses her concerns, especially as the mother of a teenager. As anti-drug messages decline and social perceptions of cannabis change, there is a need to address this issue more effectively.
In his research, Lisdahl highlights that approximately one third of adolescents who use cannabis regularly show signs of a cannabis use disorder, meaning they cannot stop using the drug despite the negative impacts on their lives. However, the lack of clarity in messaging and the growing social acceptance of cannabis complicate the task of providing conclusive information about the associated risks, even for parents, as in Lisdahl’s case.
Although it has been a decade since Uruguay officially legalized cannabis for recreational use, and other states and countries have followed this path, interpreting existing data presents significant challenges. While some studies suggest that adolescents do not use cannabis more after legalization, trends toward more problematic use are observed. This phenomenon raises crucial questions about how consumption patterns evolve and how cannabis affects adolescent brain development.
In order to obtain more definitive answers, the National Institute on Drug Abuse in Bethesda, Maryland, has funded the Adolescent Brain Cognitive Development (ABCD) study. Started in 2015, this project has recruited more than 10,000 9- and 10-year-old children to closely track their brain development over time. As these participants enter adolescence, some are beginning to experiment with cannabis, providing a unique opportunity to evaluate the impact of their use on the brain.
Despite legalization, not all places have seen an increase in teen consumption. In Colorado, for example, legalization has paradoxically led to a decline in consumption among teenagers, according to surveys conducted by the Colorado Department of Public Health and Environment. Nationally, consumption rates have also shown a downward trend, although some attribute this phenomenon to the COVID-19 pandemic.
Uruguay, the first country to legalize the sale of cannabis for recreational use, initially saw an increase in consumption among people aged 18 to 21, but these levels subsequently stabilized. Epidemiologist Ariadne Rivera-Aguirre, who conducted a survey in Uruguay, highlights that effective regulation, which includes limits on the potency of products, prohibitions on advertising and restrictions on the type of products sold, can influence the results.
Although surveys provide valuable information, some researchers emphasize the need for long-term studies like the ABCD to better understand the causal connections between cannabis use and mental health. It seeks to address crucial questions, such as why some adolescents develop problematic use while others do not, and what are the possible mechanisms at the brain level that link cannabis with mental health problems.
In this context, neuroscientist Angela Bryan highlights that the focus of research should be on understanding when occasional cannabis use becomes problematic, and not just on the frequency of consumption. As these issues are studied, there is widespread concern in the scientific community about the increasing quality and potency of cannabis products available on the market, posing additional mental health risks, especially in adolescents.
Although the association between cannabis and mental health problems, such as schizophrenia, is being studied, the director of the National Institute on Drug Abuse, Nora Volkow, highlights the need for caution and compares the risks of cannabis use with “play roulette.” As the mental health impacts of cannabis are unraveled, society faces the challenge of balancing legalization with protecting the health of adolescents and young adults.