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Marijuana’s Effects on Brain Structure and Function

Marijuana is the drug that is most commonly used by Americans over 12 years old. Very few Americans believe that chronic marijuana use can be harmful, and legalization of marijuana in some states is increasing the public’s interest in the benefits of marijuana, while potentially downplaying the risks.

The findings of a longitudinal study conducted in New Zealand proved that perhaps the risks of using marijuana at a young age are greater than many would think. In this study, 1,037 individuals were followed from birth to age 38. Neuropsychological testing was conducted at age 13 and again at age 38. The findings showed that those who used marijuana regularly displayed reduced executive function, attention, learning, memory, and motor skills that were linked to the onset age and duration of use. For those who began to use marijuana before the age of 21, abstinence from marijuana did not lead to full restoration of the brain areas that had been impacted by the previous use.

Many physicians are being faced with finding an approach to minimize harm to those under 21 due to marijuana use. Efforts to add screenings (surveys and/or drug testing) to yearly physician visits could be an effective approach to identify adolescents who use marijuana, and target those individuals with proper education and action. But, many factors such as parental consent, availability of resources, reimbursement, and what to do when an adolescent would test positive could potentially limit the feasibility of implementing this idea. However, the information in this article makes it clear that physicians advocate against marijuana use in those less than 21 years of age because of the high risk of permanent impacts on brain function.

Take away: Chronic use of marijuana in individuals under 21 may lead to irreversible abnormalities in brain maturation and cognitive function.

DeShazo, R.D., Parker, S.B., Williams, D. et al. (2018). Marijuana’s Effects on Brain Structure and Function: What do we Know and What Should We Do? A Brief Review and Commentary. The American Journal of Medicine, 131. https://doi.org/10.1016/j.amjmed.2018.09.006

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