Casual marijuana use linked to brain changes

Using marijuana a few times a week is enough to physically alter critical brain structures, according to a new study published Tuesday in The Journal of Neuroscience. "Just casual use appears to create changes in the brain in areas you don’t want to change," said Hans Breiter, a psychiatrist and mathematician who led the study.
There is actually very little research on the potential benefits and downsides of casual marijuana smoking, fewer than four times a week on average. In his study, done in collaboration with researchers at Harvard University, scientists looked at the brains of 20 relatively light marijuana users and 20 people who did not use it at all. All 40 were college students in the Boston area.
The study found volume, shape and density changes in two crucial brain areas, the nucleus accumbens and the amygdala, involved with emotion and motivation and some types of mental illness. "This is a part of the brain you do not want to mess around with," Breiter said.