Effects of marijuana on the brain still contentious

marijuana- cannabis- brainThe brains of marijuana users are different from those who don’t partake, according to a study published last week in the Journal of Neuroscience. The research found differences in brain shape among marijuana users and non-marijuana users and claimed that even casual smoking could alter the brain.

However, researchers at CSU point out that this study was not designed to determine how these changes take place, and that the actual effects of marijuana on the brain is still a very hot area of research.


“This was a small study that was not designed to determine the significance of such changes,” said Shane Hentges, an associate professor in biomedical sciences.

Marijuana certainly does affect the brain, according to Stu Tobet, a professor in biomedical sciences. Marijuana affects many areas of the brain, and the effect is often determined by the area of the brain being explored. The receptors which bind marijuana are the most abundant of their type in the brain, according to Tobet.

“With that much receptor around, it is not surprising that the ancient time-tested ‘bioassay’ for marijuana impact shows clear, strong, and reliable impact on brain function,” Tobet wrote in an email to The Collegian.

Hentges explained that marijuana binds to natural receptors, called endocannabinoid receptors, and blocks the activity of natural cannabinoids. Hentges studies these types of receptors in her lab.

When marijuana is present in the brain, normal neuronal communication is altered, according to Hentges. She said most of what is known about how marijuana affects the brain only deals with when the drug is actually present in the brain, so it is harder to measure its long-term effects.

“It is not clear from existing studies how marijuana might alter the endocannabinoid system once the drug is out of the system,” Hentges said.

Jozsef Vigh, associate professor in biomedical sciences, said that one effect of marijuana is to increase dopamine levels in the striatum, an area of the brain typically associated with reward. Vigh said this is the classic way that addictive drugs are pleasurable.

“Addictive drugs could be considered as shortcuts to ‘cheat’ the brain’s reward system,” Vigh said.

Tobet explained that often it is the concentration of the drug in the body that matters, and used another commonly used drug as an analogy.

“There is little doubt that alcohol can kill cells … there is little doubt that the majority of people enjoy alcoholic beverages,” Tobet wrote.


Tobet highlighted the need for balanced coverage of the scientific results. He said the research is varied and marijuana’s effects on the brain are determined by the area of the brain being studied, as well as the questions researchers ask.

“It is likely that we would find conditions with effects that are positive, negative and neutral,” Tobet wrote.

Tobet added that plant-based medications have been around for as long human beings, and that research into marijuana’s utility will certainly continue.

“Targeted medicinal use of marijuana components will no doubt continue to rise with the future,” Tobet wrote.

Collegian Science Beat Reporter Remi Boudeau can be reached at news@collegian.com.