Is There A Link Between Cannabis Use And Developing Dementia?

Cannabis use has risen in popularity since many states in America have either decriminalized or outright legalized the substance for sale. According to the Centers for Disease Control and Prevention, it is estimated that 18.2% of Americans, or 48.2 million people, used cannabis in 2019. By 2020, annual marijuana use among college students reached its the highest level in over thirty years, the National Institutes of Health reports.

However, the debate of whether or not using cannabis poses health risks is still being waged. There have been health benefits linked to cannabis, such as lowered blood pressure, lowered anxiety, reduced inflammation, and even fighting certain cancers, according to Johnson and Wales University. However, these benefits have been mostly linked to CBD, the non-psychoactive component of marijuana. However, the CDC reports there is mounting evidence that long-term cannabis use can cause a higher risk of psychosis and schizophrenia. There may also be a link between marijuana and developing dementia later in life.

There are a few stereotypes of people who smoke marijuana. While many of them are untrue, one that research is showing may be accurate is overall cognitive decline, including memory loss and lowered attention span. A large longitudinal study released in the American Journal of Psychiatry showed a link between long-term cannabis use and cognitive decline, lowered IQ, and "smaller hippocampal volume" — the part of your brain that plays a role in learning and memory — which are all risk factors for dementia.

The study looked at the dependence of marijuana on users starting at age 18 and measured brain functions and the size of the hippocampus at age 45. "What we're looking at here is long-term cannabis users in midlife, and we're finding that long-term users show cognitive deficits ... we're also doing a longitudinal comparison — comparing them to themselves in childhood. We saw that long-term cannabis users showed a decline in IQ from childhood to adulthood," said Madeline Meier, PhD, associate professor at Arizona State University, speaking with Medscape Medical News.

It's important to note that these individuals were studied across almost 30 years. The study made no mention of the increased risk of dementia for people who rarely smoke marijuana or who smoked regularly and then quit. While risk factors were observed in the study, additional research is needed to determine if long-term cannabis use is directly linked to dementia diagnoses in old age.