Apr 16, 2014 10:59 AM EDT By Russell Westerholm, UniversityHerald Reporter

A new study has found that casual marijuana use - a relatively un-touched research topic - can alter important portions of the human brain.

According to USA Today, researchers discovered physical brain alterations in subjects who used marijuana less than four times per week on average. The changes were seen in volume, shape and density in two areas of the brain most associated with motivation and mental illness.

"Just casual use appears to create changes in the brain in areas you don't want to change," study lead author Hans Breiter, a psychiatrist and mathematician at the Northwestern University Feinberg School of Medicine in Chicago, told USA Today. "This is a part of the brain you do not want to mess around with."

For their study, published Tuesday in the Journal of Neuroscience, Breiter's team collaborated with Harvard researchers to examine the effects of marijuana use in 20 college students from the Boston area. The research team examined the 20 students who were classified as casual marijuana smokers with 20 students who said they did not use it at all.

The marijuana-smoking students' brains were noticeably different from those who did not smoke.

"There have been a growing number of studies that suggest that marijuana use in emerging adults is associated with differences in brain structure and cognitive abilities," Staci Gruber, an associate professor of psychiatry at Harvard Medical School not involved in the study, told USA Today. "I'm not saying (pot smoking) is analogous to shooting heroin or cocaine, but it's also not quite the benign substance people thought it was."

National Organization for the Reform of Marijuana Laws (NORML) deputy director Paul Armentano told HealthDay News this study could also be used to argue for the legalization marijuana in order to regulate it. Just like alcohol and tobacco, two legal products, marijuana has adverse effects, but people use it anyway, regardless of the law.

"It's precisely because of these consequences that these products are legally regulated, and their use is restricted to particular consumers and specific settings," Armentano said.

"A pragmatic regulatory framework that allows for the legal, licensed commercial production and retail adult sale of marijuana but restricts its use among young people - coupled with a legal environment that fosters open, honest dialogue between parents and children about cannabis' potential harms - best reduces the risks associated with the plant's consumption or abuse."

See Now: Covert Team Inside Newsweek Revealed as Key Players in False Human Trafficking Lawsuit