Which is Worse for the Brain — Marijuana or Alcohol?

It appears that alcohol could be taking a greater toll on the human brain than marijuana does, particularly for teenagers, according to a brand new study.

In particular, scientists have discovered that chronic alcohol usage is connected to stark decreases in the gray matter of the brain — which contains the brain’s synapses and cell bodies — in both teenagers and in adults. And within adults, the use of alcohol was also connected to declines in the integrity of the white matter of the brain, which consists primarily of long nerve fibers that blast various messages throughout our nervous system. The use of cannabis wasn’t associated at all with either white- or gray-matter declines.

“The difference between the alcohol and the cannabis is pretty dramatic,” commented study’s lead author Kent Hutchison, who is a professor of psychology and neuroscience from the University of Colorado located in Boulder.

Marijuana and the Human Brain

This research should not be taken as an end-all in a debate whether or not cannabis is actually harmful on the brain. For starters, this study examined marijuana use only over the last 30 days, and these participants had relatively lower levels of reefer consumption. Additionally, there may also be some very subtle changes in the brain that the study was not able to capture.

However, this study did pretty much fit in with a previous body of work that revealed mixed results regarding cannabis and the human brain. There is some research on animals that implies that there are some cannabinoids, which are the compounds that resides in cannabis, may actually be protective for the body’s neural system, Hutchison added. However, studies in humans have shown varied results, and many of these studies have actually been too small to form any solid conclusions. One relatively large study that was conducted in the year 2016 found no changes in the brain’s gray matter after marijuana use, but it did find that the drug was connected to some decline in the brain’s white-matter integrity, or the quality of links among brain cells, particularly for those who began using cannabis at a relatively young age.

One of the big challenges with this kind of study is separating the use of marijuana from the use of other harmful substances, particularly alcohol, Hutchison pointed out. Another big difficulty is establishing whether or not the drug will is what’s actually causing the changes in the brain that were observed. There was a study of twins that was posted in the year 2015 which discovered that differences in the brains of pot smokers and nonusers had actually predated any marijuana use instead of being the cause of the differences. In other words, these pot smokers could have environmental or genetic factors that are predisposing them to use cannabis in the first place.

This new study had an advantage of have a very huge sample size. Scientists examined brain scans from some 850 substance-using adults that ranged in ages from 18 to 55 and also 440 substance-using teenagers ranging in ages from 14 to 19, all of which reported various levels of cannabis and alcohol use. The alcohol was the more common substance of choice, for 487 adults (57%) and with 113 teens (26%) reporting that they used alcohol only across the last six months, and 5 adults (0.6%) and 35 teens (8%) claimed they had used only cannabis over the last six months. The remaining participants used both.

Alcohol versus Pot

Hutchison and his research team had the ability to statistically control the alcohol usage factor while examining the pot effects, and also vice versa. What they discovered about alcohol use was nothing new, when you consider that booze is a well-known neurotoxin, Hutchison stated. Heavier alcohol usage always leads to bigger declines in the brain’s gray matter and also declines in the quality of link within the brain’s white matter.

By contrast, “we don’t see any statistically significant effects of cannabis on gray matter or white matter,” Hutchison commented.