Marijuana’s Negative Effects on the Brain Are Greater in Younger Users

Often, when it comes to drugs, we tend to use a sliding scale in determining their potential danger. Alcohol and marijuana are gray areas for many, who argue that they can be used responsibly. While alcohol is legal for adults and many people consume it responsibly, pot is still not legal in most states, and studies continue to show consistent marijuana use does have negative effects – and they’re worse the younger you are.

The most recent bad news for the pro-pot crowd comes from National Institute on Drug Abuse-funded research that links heavy marijuana use to adverse changes in the function and structure of brain areas associated with reward, decision-making and motivation. It’s even more dangerous for younger users, with the study showing that effects were more pronounced in brains that are still developing. It’s also important to note that for this study, “heavy” use was defined as at least four times per week in the past six months.

A recent report in the Proceedings of the National Academy of Sciences (PNAS), researchers for the first time comprehensively describe existing abnormalities in brain function and structure of long-term marijuana users with multiple magnetic resonance imaging (MRI) techniques. Findings show chronic marijuana users have smaller brain volume in the orbitofrontal cortex (OFC), a part of the brain commonly associated with addiction, but also increased brain connectivity.

So maybe those old “this is your brain on drugs” public service announcements were on to something. No drug is harmless, and the idea that a substance can be used regularly without any negative effects is just plain wrong. But the message isn’t getting out. Scientists at the Center for BrainHealth have seen a steady increase in the incidence of marijuana use since 2007. So people are smoking the drug with scarce research available to show what sort of impact it could have on public health and their own personal well being.

The study cited in PNAS was the result of research team’s study of 48 adult marijuana users and 62 gender- and age-matched non-users, accounting for potential biases such as gender, age and ethnicity. The authors also controlled for tobacco and alcohol use. On average, the marijuana users who participated in the study consumed the drug three times per day, and it took a toll.

Cognitive tests show that chronic marijuana users had lower IQs compared to age-and gender-matched controls, but the differences do not seem to be related to the brain abnormalities as no direct correlation can be drawn between IQ deficits and OFC volume decrease. The study was unique in that combined three different MRI techniques to evaluate different brain characteristics.

While the brain may try to compensate for gray matter losses initially with increases in connectivity, eventually, the wiring of the brain starts degrading as a result of prolonged marijuana use. Testing showed that earlier onset of regular marijuana use induced greater structural and functional connectivity, but the greatest increases in connectivity appear as an individual begins using marijuana. Increased structural wiring declines after six to eight years of continued chronic use. Findings also show severity of use is directly correlated to greater connectivity.

In the past, it’s been difficult for researchers to draw firm conclusions about the long-term effects of marijuana on brain structures due to limitations in methodologies, but new research methods are providing added insight. While this latest study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to age of onset and duration of use, researchers conclude.

The study is also notable in that it offers a preliminary indication that gray matter in the OFC may be more vulnerable than white matter to the effects of THC, the main psychoactive ingredient in the cannabis plant. Whether or not any of these brain changes can revert back to normal with discontinued marijuana use is still to be determined.

Further long-term studies are needed to determine the exact effects marijuana has on the brain, just how they happen and if anything can be done to repair the damage, these latest scientific findings add to the growing proof that heavy marijuana use may harm the brain.

If you or a loved one is struggling with an addiction and a co-occurring disorder, call us today. We’re available 24 hours a day, seven days a week and can provide information on treatment programs, help with insurance and answer questions about the treatment process.