Alcohol vs Marijuana: Which Is More Harmful To The Brain?

By Beth Leipholtz 02/20/18
Researchers studied the brain scans of more than 1,000 individuals to determine which substance was more damaging to the brain.
illustration of a man drinking alcohol and another smoking marijuana

When it comes to long-term effects on the brain, researchers have found that alcohol may be more damaging than marijuana, according to a new study in the journal Addiction

More specifically, researchers at University of Colorado Boulder and the CU Change Lab found that alcohol consumption was linked to long-term changes in the brain, while marijuana was not linked to any long-term changes. 

Researchers studied the brain scans of 853 individuals between the ages of 18 and 55, as well as 439 people between the ages of 14 and 18. Alcohol and cannabis use varied by individual. 

According to Science Alert, study authors wrote that alcohol use was associated with reducing the volume of grey matter in the brain. Grey matter is a substance in the brain that contains most of the brain’s neuronal cell bodies. White matter in the brain, which has to do with communication between grey matter, was also affected.

When either is damaged, the brain’s normal function can be disrupted. This was especially true for people with a long history of alcohol use, researchers found. 

“Alcohol use severity is associated with widespread lower gray matter volume and white matter integrity in adults, and with lower gray matter volume in adolescents,” study authors wrote. 

Additionally, the study found that the effects of alcohol use were worse for those over age 18. But the grey matter levels in those younger than 18 were still affected.

Still, more research is necessary in order to determine how marijuana truly affects the brain. 

"With alcohol, we've known it's bad for the brain for decades," study co-author Kent Hutchison told the Colorado Arts and Sciences Magazine. "But for cannabis, we know so little."

Because of the immediate effects of the cannabinoid, THC, in marijuana, it’s been thought that cannabis would be more damaging to the brain in the long-term. But Hutchison tells the magazine that this isn’t necessarily the case. 

"When you look at the research much more closely, you see that a lot of it is probably not accurate," Hutchison said. "When you look at these studies going back years, you see that one study will report that marijuana use is related to a reduction in the volume of the hippocampus. The next study then comes around, and they say that marijuana use is related to changes in the cerebellum or the whatever. The point is that there’s no consistency across all of these studies in terms of the actual brain structures."

Although the research showed no specific damages due to marijuana use, that does not mean it’s beneficial for the brain either. 

"Considering how much is happening in the real world with the legalization movement, we still have a lot of work to do," Hutchison said.

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Beth is a Minnesota girl who got sober at age 20. By day she is a website designer, and in her spare time she enjoys writing about recovery at, doing graphic design and spending time with her boyfriend and three dogs. Find Beth on LinkedInInstagram and Twitter.