Your Weed Is Messing With Your Memory. Science Now Says It’s Making Up New Ones Too

There’s some new research on cannabis use and memory and the aging brain making the rounds this week, and it’s interesting enough to earn your attention. As we fast approach 4/20 and all that goes with it, I thought many of you would appreciate knowing what it says.

If you live in West Hollywood the proliferation of pot shops is not news to you. I was just chuckling to myself the other day when I finally found out what was replacing a favorite nursery on La Brea. One that had been there forever, or close enough to forever. In its place, a different kind of plant shop. You can probably guess.

I live a block from another dispensary myself, which in this neighborhood isn’t really a distinction. Can’t seem to walk two blocks without catching that smell somewhere along the way. Not complaining, just noting. In fact, I love that pungent, skunky smell. 

I used to smoke weed recreationally. A long time ago, in a far away galaxy. I quit. Not for any noble reason, I simply outgrew it. Much how I stopped getting hammered on weekends. I still enjoy a rare toke poolside or for what I call “ceremony’s sake” on holiday.  But I’d been preaching forever how gross cigarettes are and what they do to your lungs. I had to ask myself what exactly I thought I was doing putting any kind of combustion smoke in my lungs. Gummies? Nah. Y‘all enjoy. No judgement here. I get it, enjoy.

Either way, actual research is now catching up to a pretty basic question: what does regular weed use do to your brain when you’re in your 40s, 50s, 60s? The Washington Post pulled it together this week. Some of what it says is pretty interesting, especially if you’re over 40.

The hit to your memory is real. So put the bong down and take a look, cause the problems don’t all just go away when you sober up. 

Working memory is the ability to hold a piece of information in your head for immediate use. A phone number, the name of someone you just met. The thing you walked into the kitchen to get. Cannabis affects it acutely, most people who have ever used it already know that.

What’s newer is what long-term use does. A January 2025 study in JAMA Network Open — the largest of its kind — looked at brain imaging data from more than 1,000 adults between 22 and 36. Heavy lifetime users showed lower brain activity during working memory tasks than nonusers, even when people who’d used recently were excluded from the analysis. I know this will come as no surprise to many. The point is, the data and facts are in – this is your brain on drugs.

A 2026 study out of Washington State University adds a wrinkle that’s somehow worse. It’s not just that you forget things. It’s that you may remember things that never happened, and feel completely certain about them. Researchers gave 120 cannabis users either real THC or a placebo, then ran them through 21 memory tests. Seventy percent showed some level of impairment. The standout finding was false memory: confident recollection of events or details that simply didn’t occur.

The explanation is that THC weakens accurate recall while leaving the sense of familiarity intact. Your brain fills the gap and hands you something wrong. “If you blast the system with THC, the THC hijacks the system,” said Carrie Cuttler, an associate professor and co-author of the study. The good news, such as it is: most of those acute effects clear up after about a month of not using.

“If you smoke cannabis, afterward, if you do a working memory test where you’re trying to maintain some piece of information, like a phone number or a short list of words, you’re less good at doing that while you’re acutely intoxicated,” said Joseph Schacht, associate professor of psychiatry and co-director of the Division of Addiction Science, Prevention and Treatment at the University of Colorado School of Medicine. Consistent users show lasting deficits compared to nonusers, he said.

No established link between cannabis use and dementia risk has shown up in the current data. Researchers say the studies are still too small and too short to settle that question either way.

When you started matters more than how much you use

Long-term cannabis use has been linked to changes in brain volume. How that plays out depends heavily on how old you were when you first started.

People who began using in adolescence show the most pronounced effects — particularly in white matter, the tissue that connects different brain regions and helps them communicate. Younger users show more difficulty with executive function and inhibition control, according to research by Staci Gruber, director of Marijuana Investigations for Neuroscientific Discovery at McLean Hospital and associate professor of psychiatry at Harvard Medical School.

“Cannabinoid exposure during that developmental window probably interferes with some of those normal brain development functions,” Schacht said.

A 2026 meta-analysis of 77 studies in the journal Addiction found cannabis use was associated with reduced volume in the amygdala, the region involved in processing and regulating emotions. That study didn’t include data on age of first use.

Adults who started using after roughly age 25 show a different picture entirely. In research published this year in the Journal of Studies on Alcohol and Drugs, adults between 40 and 70 who came to cannabis in adulthood actually showed greater brain volume compared to nonusers. That was especially true in areas of the brain dense with cannabinoid receptors. The researchers described it as potentially “neuroprotective,” given that brain shrinkage is a normal part of aging and is linked to cognitive decline.

Mood: not as simple as the product descriptions

A lot of people use cannabis for anxiety, to help them sleep, deal with their depression, or just the daily edge. Back in the day, I simply used it to get high. To enjoy the fuzzy buzzy that came along with the ride. The science on whether that actually does the trick and helps with the things I mentioned is murkier than any dispensary menu implies.

The Lancet Psychiatry looked at THC and CBD in relation to anxiety, PTSD, depression and bipolar disorder. The bottom line: no clear evidence of help or harm for most conditions. Not enough data on others to say much.

Gruber said the research framing may be part of the problem. Studying isolated compounds rather than the whole plant misses how everything interacts. “The synergistic action of these things all together is significantly greater than the sum of its parts,” she said.

Schacht was more direct about using cannabis for mood over the long term. “Depression and anxiety are frequently reasons that people use a number of substances, such as cannabis, alcohol and nicotine,” he said. “Those drugs can be helpful in relieving those symptoms in the short term, but over the long term, I think it’s fairly clear that they are not helpful and, in some cases, actually exacerbate the problem that led people to turn to them in the first place.”

The research can’t move as fast as the industry does

Cannabis is still a Schedule I controlled substance at the federal level, sitting in the same regulatory category as heroin and LSD. That limits how researchers can study it. Administering the drug to test subjects in a lab setting is essentially off the table.

“It would be so much easier if people could use those things in the laboratory, for example, but we can’t generally do that,” Schacht said.

Basic questions remain unanswered. Whether it matters whether you smoke it, vape it or eat it — in terms of cognitive effects — is still an open research question. Long-term data on older users (60+) is thin, even as this group has become the fastest-growing group of cannabis users in the country.

So until then, enjoy. Just wonder no more why you can’t find your keys. Or why you’re absolutely certain you already fed the dog – oh wait, you don’t have a dog. 😳🤡🤦🏻‍♂️​​​​​​​​​​​​