Is It Really True That Marijuana Makes You Dumb?

From Fast Times at Ridgemont High to Harold and Kumar Go to White Castle, the stereotype of the stupid stoner has featured prominently in the media over the past several decades. But is there any truth to this portrayal? Does consuming marijuana make you dumb? The short answer is: no, not really.

In a study published last month in JAMA Psychiatry, University of Pennsylvania researchers found that a small reduction in cognitive functioning occurred in individuals who reported frequent marijuana use. However, those who abstained from cannabis for more than three days registered no significant change in memory, judgment or rational thinking.


The study’s findings are based on a comprehensive review and meta-analysis of 69 studies conducted over the past 45 or so years involving adolescents and young adults. These cross-sectional studies included 2,152 frequent or heavy cannabis consumers along with 6,575 control subjects.

Previous Studies Showing Decline in IQ Due to Cannabis Are Off the Mark

In regard to the small reduction in cognitive functioning, researchers noted that it “may be of questionable clinical importance for most individuals. [R]esults indicate that previous studies of cannabis youth may have overstated the magnitude and persistence of cognitive deficits associated with marijuana use.”

Those previous studies include a 2012 Duke University study comparing the IQs of individuals spanning the ages between 13 and 38; it concluded that heavy cannabis intake during adolescence and early adulthood was to blame for lowered IQs. That study has since been debunked as it didn’t take into account other key factors such as existence of trauma or abuse.


Why Does Abstinence Bring the Cognitive Loss From Heavy Cannabis Intake to Zero?

HelloMD’s Chief Medical Officer Perry Solomon, M.D., echoes the researchers’ conclusions, by saying, “It’s interesting that, in fact, the study did show a small but significant overall decline in cognitive function, though this may not bear much weight. The more interesting part of the study is that abstinence lasting longer than 72 hours brings the loss [in cognitive function] to zero.”

He adds, “We need further studies to figure out why cognitive decline is negligible with abstinence. Does the effect of cannabis wear off, or is it due to some regenerative healing that results in no cognitive loss?”

Indeed, additional research is needed to better understand exactly how cannabis interacts with and influences multiple systems in the body, including in the brain. So far, the preliminary research is proving to be promising. When it comes to marijuana’s therapeutic effects, they’re varied and abundant—from that of anti-inflammatory and analgesic to neuroprotectant and more.

Photo credit: Sharon McCutcheon

If you’re new to cannabis and want to learn more, take a look at our Cannabis 101 post. HelloMD can help you get your medical marijuana recommendation; it’s easy, private and 100% online.


Related Articles

The perfect dose of cannabis content

Delivered right to your inbox.

Scroll to Top