Research on the Effects of Marijuana

Peter Lear, LCSW, RYTBy Peter Lear, MSW, LCSW, RYT

Cannabis is becoming decriminalized and legalized in an increasing number of states and this trend will only continue. As marijuana gains even greater mainstream acceptance, it is likely that more young people will try, experiment with, and regularly use cannabis. Some will abuse it and others will become addicted. Pro-marijuana groups in particular claim that marijuana is not addictive. Dr. Leslie L. Iverson, a professor of pharmacology at the University of Cambridge in England has studied marijuana extensively and his research demonstrated that approximately 10 to 13% of marijuana users will become addicted.

Marijuana Affects the Brain

New research indicates that even moderate use has measurable effects on the brain. This research, published in the Journal of Neuroscience from Harvard and Northwestern Universities, studied the brains of 18- to 25-year-olds, half of whom smoked pot recreationally and half of whom didn’t. What they found was rather shocking: Even those who only smoked a few times a week had significant brain abnormalities in the areas that control emotion and motivation.

“There is this general perspective out there that using marijuana recreationally is not a problem — that it is a safe drug,” said Anne Blood, a co-author of the study. “We are seeing that this is not the case.”

Researchers evaluated two basic types of cannabis users: those who used it four times or more per week and those who used it once per week.

Using three different neuroimaging techniques, researchers then looked at participants’ nucleus accumbens and amygdala. These areas are responsible for gauging the benefit or loss of doing certain things, and providing feelings of reward for pleasurable activities such as eating, having sex and interacting socially.

“This is a part of the brain that you absolutely never ever want to touch,” said Breiter. “I don’t want to say that these are magical parts of the brain — they are all important. But these are fundamental in terms of what people find pleasurable in the world and assessing that against the bad things.”

Even Infrequent Use Has Consequences

Shockingly, every single person in the marijuana group, including those who only smoked once a week, had noticeable abnormalities, with the nucleus accumbens and the amygdala showing changes in density, volume, and shape. Those who smoked more had more significant variations.

Researchers admit their sample size was small and they need to gather more data from a larger sample size, but preliminarily people (especially young people) need to be careful with this powerful drug.

“People think a little marijuana shouldn’t cause a problem if someone is doing OK with work or school,” said Breiter. “Our data directly says this is not so.”