Impaired memory functions from marijuana use don’t have to be permanent.
New research on the impact of marijuana use among teenagers appears to corroborate other studies that suggest cannabis can be detrimental to the development of their brains.
However, the recent study also suggests that abstinence from marijuana use for 30 days or more may reverse its effect on memory, attention and the ability to retain new information.
The results of the research have raised additional questions about marijuana use and teenagers, including the possibility of permanent impairment if no abstinence is undertaken.
As Science News noted, studying marijuana use among this age group runs afoul of ethical issues—unlike adults, children can’t be asked to use a drug in order to study its effects. So the researchers—from Massachusetts General Hospital in Boston and Harvard Medical School—circumnavigated the problem by recruiting teenagers who reported using marijuana at least once a week to participate in their study.
Eighty-eight Boston-area teens and young adults between the ages of 16 and 25 who reported weekly marijuana use were recruited, and 62 of them were offered money to stop using for a month. Payments increased as the month wore on, with some participants earning more than $500 for their abstinence.
Of the 62 that received payment, urine tests revealed that 55 of them were able to remain abstinent for the full 30 days. All 88 test subjects were also tested on levels of attention and memory; these included directional tests and the monitoring of number sequences, as well as retention of information.
The study results—which were published in the Journal of Clinical Psychiatry on October 30—found that while attention remained largely unchanged for the abstinent participants, they showed moderate improvement on memory tests, especially those that required them to remember lists of words. Those participants that continued to use marijuana during the test period showed no signs of improvement on these memory tests.
Neuropsychologist and study co-author Randi Schuster said that the test results showed that marijuana use can have a negative impact on how young people retain new information, but abstinence may play a role in reversing those effects. “From these data, we think that at least some of that impairment is not permanent,” she noted.
Response to the study results focused on the effect of marijuana use beyond the study time frame. “If somebody is using very heavily over a prolonged period of time, is there a point at which these functions may not recover?” asked clinical neuropsychologist April Thames of UCLA.
To answer these questions, Schuster and her fellow researchers plan additional, longer-term studies, including studying the effect on memory among 13- to 19-year-olds who abstain for a period of six months.
