Study suggests tentative link between teen pot use and IQ

A study published in a Scandanavian medical journal suggests there could be a link between heavy marijuana usage in teens and lower IQ scores.

The researchers called the findings “tentative” because of a small sample size and said they would need to be “verified with a larger study with more participants.”

The study, published last week in the peer-reviewed journal Acta Psychiatrica Scandinavica, was done by a team of researchers in London, Ontario. It comes a month before voters in Nevada and four other states decide whether to legalize the recreational use of marijuana in the Nov. 8 election.

Researchers from Lawson Health Research Institute and Western University, both in London, Ontario, examined a group of 74 teenagers younger than 17, aiming to determine whether marijuana use helped with depression symptoms.

Teens were split into four groups: frequent marijuana users suffering from depression, frequent marijuana users without depression, those with depression who were not marijuana users and teens who said they were not depressed and did not use marijuana.

The groups were put through psychiatric, cognitive and IQ testing and brain scanning. The study found that marijuana didn’t improve depression symptoms.

The study also found that early marijuana use was associated with lower IQ.

Marijuana opponents in Nevada say the study shows why Question 2, which would legalize recreational marijuana for adults 21 and over, is bad for the state.

“This study is yet more evidence that marijuana use badly affects educational outcomes and hurts our kids’ chances of success,” said Pat Hickey, spokesman for Protecting Nevada’s Children, the political action committee that is opposing the Nevada marijuana legalization effort.

Marijuana supporters say making those assumptions from such a small study is “fishing for a misleading result.”

“Just like you can find studies that disprove climate change, you can find studies that prove any point you want to make. But the general consensus is that marijuana use does not appear to lower IQ,” said Joe Brezny, spokesman for Regulate Marijuana Like Alcohol, the political action committee sponsoring the legalization effort.

Brezny pointed to a much larger study done in 2014 by the University College of London. That study examined the IQ of 2,612 8-year-olds in the United Kingdom and then again at 15. It found “no relationship between cannabis use and lower IQ at age 15,” when other factors like alcohol use, cigarette use and other circumstances were factored in.

The 2014 study found a link between alcohol use and lower IQ.

Brezny noted that Question 2 would legalize marijuana only for adults 21 and over and said a big goal of the effort is to keep marijuana out of teenagers’ hands.

“We all want to prevent teen marijuana use. And marijuana prohibition is the worst possible system for that. Not only do street dealers make it easily available, but they also offer teens more dangerous drugs,” he said. “We need to get marijuana off the streets and into regulated stores that check IDs.”

Contact Colton Lochhead at clochhead@reviewjournal.com or 702-383-4638. Follow @ColtonLochhead on Twitter.