A new study says that long-term cannabis users are likely to harbor structural brain abnormalities.
The new study led by Murat Yucel, Ph.D., M.A.P.S., of Orygen Research Centre and the Melbourne Neuropsychiatry Centre at the University of Melbourne, Australia has revealed that long-term cannabis use may lead to structural abnormalities in areas of the brain known as the hippocampus and amygdala.
Hippocampus is that area of brain, which regulates emotion and memory, while amygdala plays a primary role in with fear and aggression.
"Although growing literature suggests that long-term cannabis use is associated with a wide range of adverse health consequences, many people in the community, as well as cannabis users themselves, believe that cannabis is relatively harmless and should be legally available," wrote the authors.
Yucel along with colleagues from the University of Wollongong performed high-resolution structural magnetic resonance imaging on 15 men with an average age 39.8 years and smoked more than five joints daily for more than 10 years.
The results were then compared with images from 16 individuals with an average age 36.4 who were not cannabis users.
All participants also took a verbal memory test and were assessed for sub-threshold (below the standard of disease diagnosis) symptoms of psychotic disorders, which include schizophrenia and mania.
The hippocampus and the amygdala tended to be smaller in cannabis users than in controls as its volume was reduced by an average of 12 percent in the hippocampus and 7.1 percent in the amygdala.
"There is ongoing controversy concerning the long-term effects of cannabis on the brain," the authors write.
"These findings challenge the widespread perception of cannabis as having limited or no neuroanatomical sequelae. Although modest use may not lead to significant neurotoxic effects, these results suggest that heavy daily use might indeed be toxic to human brain tissue.
"Further prospective, longitudinal research is required to determine the degree and mechanisms of long-term cannabis-related harm and the time course of neuronal recovery after abstinence," the authors added.
The report is published in June issue of Archives of General Psychiatry, one of the JAMA/Archives journals.