Study questions the idea that cannabis use is more harmful to adolescents

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Courtesy of Lift Magazine

Many concerns have been raised about adolescent cannabis use. Adolescence constitutes a sensitive period of brain development, which some have hypothesized could be disrupted by the effects of cannabis. In specific, there is a concern that the well-established acute effects of the drug on cognition and emotion could translate into long-term deficits for those who start consuming at a young age.

According to the authors of a recent study, there is still a great deal of controversy surrounding this topic. The long-term cognitive effects that have been detected are generally of small magnitude, and many subdue after abstinence or are explained by other habits such as tobacco use (as we discussed in previous Lift reviews about the effects of cannabis on memory and school performance). In addition, the studied samples are rarely representative of adolescent cannabis users, as they use either older university students or patients from drug treatment facilities.

To get beyond these limitations, Dr. Cobb Scott and colleagues from the Perelman School of Medicine at Pennsylvania University looked at data from a large representative sample of nearly 5.000 youths aged 8 to 21. The authors collected data about cannabis and other substances which they then compared with performance via a batch of neurodevelopmental tests measuring aspects of attention, memory, complex reasoning and emotional intelligence.

Contrary to what they expected, the 5% of youths who fulfilled the criteria for frequent cannabis use (three or more times per week over the past year) performed slightly worse than non-users (74% of the sample) only on ‘executive control’ tasks, which very generally require sustained periods of attention and an ability to manipulate mental information. In addition, the group differences were small and largely confined to younger ages (age 14-17), with older youths (18-21) showing no sign of deficits. There were no performance deficits among frequent users in the remaining domains.

Even more surprisingly, the data showed that occasional users (using two or less times per week over the last year, 21% of the sample) actually performed better than non-users in the same executive control tasks, as well as in tests probing into long-term memory and emotional intelligence.

It is necessary to emphasize that these findings are correlational in nature; therefore, we do not know whether cannabis in small amounts improves cognitive and emotional performance, or if young people who already exhibited such traits are more likely to partake in occasional cannabis use. Here is what the authors had to say about this:

“Enhanced social cognition associated with occasional cannabis use may relate to the social context of use, which is often driven by peer interactions and influences. In other words, obtaining cannabis as an adolescent may involve enhanced social functioning.”

The results from occasional users were also substantially attenuated after controlling for other drug use and psychopathological and socio-economic variables. Although this argues against any ‘enhancing’ effects of cannabis, it still makes a strong case that cannabis in small amounts is relatively safe for the average young user.

The authors call attention to the fact that, however small, the cognitive effects detected in their study can still be clinically relevant for a given individual—an aspect that should not be ignored by public health policy makers.

One big limitation of this study should be noted: the measures of cannabis and other drug use consisted of one single question that relied on personal recall. It is doubtful that participants could discriminate very accurately between frequent (3 or more times per week) and occasional use (2 or less times per week), raising questions about the study’s conclusions. Hopefully future studies will fix this issue and provide a more definitive answer to the question of cannabis use in adolescence.

The work described in this piece was funded by the U.S. National Institute of Health and the Dowshen Program for Neuroscience, and can be retrieved from the journal Psychology of Addictive Behaviors.

Featured image via US Department of State.

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