Cannabis might disrupt brain development in early adolescence – but it could actually improve memory and cognitive function in older adults.
In a 2021 study, at the University of Vermont and his colleagues compared brain scans of nearly 800 teens taken five years apart. They found that adolescents who reported using cannabis during that time period experienced .
A follow-up study published last year, involving a different group of volunteers, all aged 22, who had used cannabis as teenagers, suggested that . This hints at a critical window during which the drug can disrupt neurological development.
Advertisement
The region of the brain that appeared to have thinned the most in adolescent cannabis users is involved in impulse control, says Albaugh. However, he notes that a certain amount of cortical thinning is normal in teens. The correlation might therefore be a chicken-and-egg problem: it could be that teens who tend to be more impulsive because of their naturally thinner prefrontal cortices are more likely to use cannabis, rather than the other way around.
The science of cannabis
As the use of marijuana and its compounds rises around the world, żěè¶ĚĘÓƵ explores the latest research on the medical potential of cannabis, how it is grown and its environmental impact, the way cannabis affects our bodies and minds and what the marijuana of the future will look like.
But while marijuana might negatively impact young, developing brains, there is growing evidence suggesting that it may have positive effects in older adults. This could be related to the effects that age has on the body’s endocannabinoid system – the complex network of receptors that interacts with molecules in cannabis.
“The interesting thing about ageing is that the endocannabinoid system itself changes developmentally,” says at the University of Colorado Boulder. “We have fewer cannabinoid receptors as we get older, more when we’re younger.”
Bryan and her colleagues studied 196 adults aged 65 or older, 43 of whom used cannabis at least once a week. These regular cannabis users had than the non-users. The researchers didn’t explore whether this translated to better performance on cognitive and memory tests, .
Bryan’s team then analysed MRI brain scans taken from some of the volunteers and also from a group of young adults between 25 and 35 years old who didn’t use cannabis. It turned out that the older volunteers who used cannabis were more likely than their abstaining peers to have brains that resembled the younger volunteers.
Additionally, says Bryan, research in elderly mice has demonstrated that exposure to tetrahydrocannabinol (THC) – the main psychoactive ingredient in marijuana – could actually reverse damage to memory-related brain structures.
It is still unclear whether these positive and negative developmental effects are universal, or whether certain people may be genetically predisposed to them. “There’s clearly a lot of individual variation,” says Albaugh. Future research may help determine who should use cannabis for their health, and when.
