Effects of Weed on the Teen Brain Might Be 'Overstated,' Study Says

How marijuana affects the brain has long been debated. While previous studies determined it's detrimental to the development of teenage brains, a new study suggests the negative long-term impacts of weed might be minimal.

In the new study, researchers set out to better understand the possible risk of frequent cannabis use and cognitive function among teenagers and young adults. Their research, which was sparked by the shifting cultural views and policy changes surrounding the drug, found that cognitive effects exist, but may not last long.

The meta-analysis, published in JAMA Psychiatry, analyzed data from 69 previous studies, authored between 1973 and 2017, that focus on heavy recreational marijuana use and cognitive function in more than 2,000 young people, a majority of whom were male. An additional 6,500 participants who were non-users were also included in the research as comparison participants.

They found that participants who said they were heavy marijuana users were more likely to have lower scores than non-users on a number of cognitive domains including attention, speed of information processing and delayed memory.

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A man is pictured with marijuana, rolling a joint. Pedro Pardo/AFP/Getty Images

However, they also found that heavy users who laid off weed for about 72 hours had a cognitive effect that faded.

"That was the biggest surprise," J. Cobb Scott, assistant professor of psychiatry at the Perelman School of Medicine at the University of Pennsylvania, told TIME. "There is biological plausibility that cannabis could cause changes in the brain that is still developing. But the abstinence data we have indicates that while those effects are detectable, they seem to go away after more than three days of abstinence."

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Scott and his colleagues conclude that previous research of marijuana use among youth "may have overstated the magnitude and persistence of cognitive deficits associated with use."

Although the potentially temporary effects might be reason to celebrate for pot users, it's important to note that their findings can only assess correlation, not causation.