Mother Knows Best: What Long-Term Effects Does Cannabis Have on the Brain?

Dear Mother,

I am pro-legalization across the United States and an occasional smoker. I'm married to a major, yet highly functioning stoner. He has a great paying job and when stoned, he doesn't just sit on the couch playing video games and munching. He smokes five to seven times per day and I wonder if there is any research on long-term effects of chronic marijuana smoking that aren't done by opponents of pot. I'm much more interested in what effects it has on the brain and mood over what it might do to sperm counts in men, or lung and heart problems. Have you come across this kind of research?

— L. R.

Dear L.R.,

I completely understand your concern regarding long-term health effects. While it can be tricky to parse through the evidence (what is legitimate and what are pure scare tactics?!), I will do my best to help give you a better idea of the information that is out there.

A study that was released in 2014 received some media attention as it examined 20 years of research on both acute and chronic effects of cannabis on regular users. The study was published in the journal Addiction, and does have a heavy focus on addiction and withdrawal. However, the study does go into other chronic use effects.

One of the main takeaways—for me at least—was that a lot of these potential effects are only things that "may" happen, and I believe a lot of that probability has to do with amount of cannabis used, how it's consumed (smoking flower vs. vaping, edibles, etc…), and the quality of the marijuana being used. That said, according to this study, cannabis could have an effect on the following aspects of a chronic users’ health when it comes to brain and mood:

Cannabis has a link (albeit a small one) to schizophrenia.

The study showed a causal relationship between marijuana and schizophrenia, estimating that use of the plant might double the risk of the mental illness (from 7/1,000 in non-users to 14/1,000 in chronic users). However, the study also acknowledged that those who quit cannabis after experiencing their first psychotic episode will have fewer symptoms and an easier time moving forward.

There is an increased risk of various psychotic symptoms.

This one is tricky, and the study recognizes that there might be a chicken/egg scenario happening here. Do chronic cannabis users have a higher risk of experiencing psychotic symptoms (delusions, hallucinations, disordered thinking, etc…) or do those who experience psychotic symptoms find some sort of relief in using cannabis?

There may be a risk of cognitive decline.

The study found that IQs of longtime users dropped eight points, with those who began using cannabis as teenagers having the most significant decline. However, there was also evidence that once users stopped using cannabis, there was no evidence of any decline a year later.

The study found that cannabis is linked to reduced learning, memory, and attention, which is interesting since the plant can be helpful in treating ADD/ADHD. So, take all of this with a grain of salt. Know that, yes, there is probably some connection between mental health, mood, etc. and cannabis use. For some, cannabis can be helpful! For others, it may cause issues. However, the same can be said of many long-term medications that are out there—and that have more significant negative impact on health!

And don't forget, as cannabis becomes legal in more states—and hopefully at a federal level one of these days—there will be better studies and more data to draw from, giving us more important and useful information!

— Mother