Study Says Marijuana may Lower IQ

The million dollar question: does marijuana really have negative long-term effects?

The Brain Drain

For years, scientists have been debating whether marijuana use has negative long term effects on the brain. Over two decades and 1,037 participants later, we just might have the evidence to prove that marijuana does indeed cause cognitive decline.

A study published in the Proceedings of the National Academy of Sciences in August 2012 asserts that teens who started using marijuana before age 18 and were diagnosed as being addicted to cannabis by age 38 experienced an IQ drop of 8 points–enough to fall from the 50th percentile to the 29th percentile.

This two-decade-long study followed 1,037 children born in the town of Dunedin, New Zealand. Authors administered IQ tests to individuals at age 13, and then again at age 38. During the years in between, they controlled factors like years of education, other mental disorders, use of alcohol or other drugs that might have an effect on IQ.

In addition, friends and relatives were also required to fill out a questionnaire confirming that the user indeed did show memory and attention problems at home or work.

The results were clear enough: long term use of marijuana through the teen years and into early adolescence caused an IQ drop of 8 points. In contrast, those who never used marijuana showed no decline in IQ.

The study also found that those who used marijuana heavily before age 18 showed mental decline even after they quit taking the drug, proving how drug use during a time when the brain is still growing and changing–namely the teenage years–can have a lasting impact on the brain.

With the upsurge of support for marijuana legalization during the past election, it’s not surprising that many skeptics have tried to poke holes through the study to undermine the conclusions. While the study is not without its weaknesses, many still agree that these authors have presented a thorough, well-conducted study with clear results.

A greater risk

This study provides some compelling evidence against long-term marijuana use, yet science has already proven that marijuana causes significant brain changes. Marijuana is an addictive drug, and the process of addiction includes a complicated series of neurobiological changes in the brain.

Perhaps you have heard people vaunt their stories about how they smoke weed three times a day “and I’m still not addicted!”  And that may be partly true: marijuana does not cause strong physical dependence, which means it does not induce strong withdrawal symptoms when users “quit using”.

However, marijuana is psychologically addictive, and the psychological craving can be overwhelming.

Studies show the chances of addiction are highest among regular users and–no surprise–teen users. According to the National Institute on Drug Abuse, 1 in 6 teens who smoke marijuana will become dependent on it. This number rises to 25-50 percent among daily users.

…And they know it not

Yet the evidence matters not to those whom it should matter the most. An increasing number of teenagers are smoking weed, and even  more see no long-term harm of regular marijuana use.  According to the Monitoring the Future survey published just this month, 1 in 15  of high school seniors smoke marijuana on a daily or near daily basis.

This study also finds that teen perception of marijuana harmfulness has reached an all time low: only 44% of high school seniors perceive regular use of marijuana harmful–a historic low in the history of Monitoring the Future surveys.

Regular marijuana use is preventing too many young people from reaching their full potential.” -Dr. Gaya Dowling chief from the Science Policy Branch at the National Institute on Drug Abuse.

Partnering to Protect

Duffy’s stands for the prevention of marijuana abuse among teens, and we are here for the parents, teens, and friends who are seeking help or answers about drug use or addiction.

If you or a loved one have any questions about marijuana abuse or addiction, feel free to chat with a representative or call us at 707.200.6968.