The memory and thinking abilities of teenagers do not appear to be as strongly affected by weed consumption as previously suspected, according to an evaluation of data from dozens of previous studies. \n These fears have been overstated, according to research published on April 18 in the journal JAMA Psychiatry , which suggests that while cognitive effects may be significant, they do not last very long, even among chronic users…after 72 hours of abstinence. \n While studies have shown that marijuana is 114 times less harmful than alcohol , marijuana’s impact on adolescents’ brain development and mental health has been used as fuel for anti-cannabis policy makers and worried parents. \n But it now appears that these studies may have just been identifying impairment caused by residual effects of the cannabis or withdrawal symptoms. \n This was also the first of such a study undertaken specifically with teens and young adults. \n "There have been a couple of meta-analyses done in adult samples, but this is the first one to be done specifically in adolescent and young adult samples," said Cobb Scott, assistant professor of psychiatry at the Perelman School of Medicine at the University of Pennsylvania and a lead author of the study. \n “In light of the changing perceptions of cannabis use and an evolving policy landscape surrounding cannabis, understanding the potential risks of cannabis use for mental health and brain functioning is of paramount importance,” the authors conclude . \n For the review, Scott and his colleagues pooled data from 69 studies involving more than 2,100 pot users. The ages of participants ranged from 18 to 30 in most of the included research. \n “[Our] results indicate that previous studies of cannabis in youth may have overstated the magnitude and persistence of cognitive deficits associated with use.” \n That could be an indication "that some of the effects found in previous studies may be due to the residual effects of cannabis or potentially from withdrawal effects in heavy cannabis users," Scott said.