Teens’ memory harmed by pot
A new study shows another reason why marijuana and teens just don’t mix.
The study, published in the Hippocampus journal, found that teens who were heavy marijuana users also had an abnormal shaped hippocampus and performed poorly on long-term memory tasks.
“The memory processes that appear to be affected by cannabis are ones that we use every day to solve common problems and to sustain our relationships with friends and family,” senior author Dr. John Csernansky, of Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital, said in a press release.
Heavy marijuana users in the study were defined as 16 and 17 year old teens who smoked daily for about three years.
A total of 97 people participated in the study, which included matched groups of healthy controls – participants who abused marijuana, schizophrenic participants with no known history of substance abuse, and schizophrenic participants who abused marijuana.
The participants were monitored during their early twenties, required to have stopped smoking marijuana for at least two years and did not abuse other drugs.
The study involved people taking a memory test where they listened to a series of stories for about one minute. Roughly 20 to 30 minutes after listening, participants were asked to recall as much content as they could remember.
The results showed that young adults who abused cannabis as teens performed about 18-percent worse on long-term memory tests than young adults who never abused cannabis.
They also found that the longer the individuals were chronically using marijuana, the more abnormal the shape of their hippocampus. The findings suggest that these regions related to memory may be more susceptible to the effects of the drug the longer abuse occurs.
According to a National Institute on Drug Abuse study in 2014, marijuana use remained stable among teens. In the past month, 6.5 percent of eighth-graders reported using marijuana, 16.6 percent among 10th-graders and 21.2 percent among 12th-graders.
Although marijuana use has remained relatively stable over the past few years, the majority of high school seniors do not think occasional marijuana smoking is harmful, with 36.1 percent saying that regular use puts the smoker at greater risk. Marijuana use continues to exceed cigarette use in all three grade levels, according to the study.
Study leaders suggest more long-term research is needed to confirm their findings.
“Because the study results examined one point in time, a longitudinal study is needed to definitively show if marijuana is responsible for the observed differences in the brain and memory impairment,” lead study author Matthew Smith said. “It is possible that the abnormal brain structures reveal a pre-existing vulnerability to marijuana abuse. But, evidence that the longer the participants were abusing marijuana the greater the differences in hippocampus shape suggests marijuana may be the cause.”
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