Exclusive: Effects of cannabis use in adolescents may not last long, new research finds

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Research about the effects that cannabis use has on adolescents and young adults often yields inconsistent results. Typically studies show a strong correlation between marijuana consumption and reduced cognitive functioning but new research is showing that these cognitive effects may not persist for very long even for chronic users.

JAMA Psychiatry published the findings from their meta-analysis that combined data from previous studies, all which examined the effects of heavy marijuana consumption on cognitive functioning in adolescents and young adults.

The meta-analysis included information from 69 previous studies and compared 2,151 frequent marijuana users with 6,575 non-users aged 10-50 with an average age of 21.

“There have been a couple of meta-analyses done in adult samples, but this is the first one to be done specifically in adolescent and young adult sample,” said Cobb Scott, assistant professor of psychiatry at the Perelman School and Medicine at the University of Pennsylvania and a lead author of the study. “We looked at everything from learning and memory to different aspects of executive functioning such as abstraction ability, and we basically show that the largest effects—which was around a third of a standard deviation—was in the learning of information and some aspects of executive functioning, memory and speed of processing.”

The research found that heavy marijuana users scored lower than non-users in cognitive domain such as learning, abstraction, speed of processing, delayed memory, inhibition and attention. However, when the studies were separated based on length of abstinence, differences in cognitive functioning were not apparent after 72 hours.

The studies were also separated by length of marijuana abstinence, age of first cannabis use, sociodemographic characteristics and clinical characteristics like depression to identify factors that could have affected the relationship between marijuana use and cognition.

After examining these factors, it was only the length of abstinence from marijuana that was found to affect the association between heavy use and reduced cognitive function. 72 hours seems to be the threshold identified in previous studies.

According to Scott, this could be an indication that effects found in previous studies may be due to the residual effects of cannabis withdrawal in heavy users.

While marijuana remains illegal at the federal level, it is difficult to perform research, but as more states look toward legalization, the research will be absolutely necessary to ensure responsible implementation of the substance. The research, while positive, underscores the fact that more research needs to be done in this area.

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