Cancer patients who use cannabis to address their symptoms have less pain and sleep better, according to new University of Colorado Boulder research. But they also experience another, unexpected, benefit: After a few weeks of sustained use, they seem to think more clearly.

“When you’re in a lot of pain, it’s hard to think,” said senior author Angela Bryan, a professor of psychology and neuroscience at CU Boulder and a cancer survivor. “We found that when patients’ pain levels came down after using cannabis for a while, their cognition got better.”

The small but groundbreaking study, published April 26 in the journal Exploration in Medicine, is among the first to assess how cannabis bought over the counter at dispensaries— rather than government supplied or synthetic cannabis — impacts cancer symptoms or chemotherapy side- effects.

The study also explored the variety of products cancer patients use now that it is legal in most states.

Bringing the lab to the patients

Surveys suggest that as many as 40% of U.S. cancer patients use cannabis, yet only a third of doctors feel comfortable advising them about it.

Studying it is complicated, because federal law prohibits university researchers from possessing or distributing cannabis for research unless it’s government-issued or of pharmaceutical grade. As a result, most studies have looked only at prescription products like nabilone or dronabinol (typically prescribed for nausea) or government cannabis strains that tend to be less potent and lack the variety of over-the-counter offerings.

This research team took a different approach.

Bryan collaborated with oncologists at the CU Anschutz Medical Campus to observe 25 cancer patients who used cannabis over two weeks. 

After a baseline appointment in which their pain levels, sleep patterns and cognition were assessed, they were asked to purchase the edible product of their choosing from a dispensary. Choices were surprisingly varied, spanning 18 brands, including chocolates, gummies, tinctures, pills, and baked goods, and contained varying ratios of THC and CBD at a wide range of potencies. 

“This tells us that people are open to trying whatever they think might be useful, but there's just not much data out there to guide them on what works best for what,” said Bryan.

To study acute impacts, researchers drove a “mobile laboratory” (a Dodge Sprinter van sometimes referred to as the “cannavan”) to each patient’s home one day. Participants underwent physical and cognitive assessments in the van, then re-tested in the van after using cannabis in their homes.

After two weeks of sustained use at the frequency of their choice, they also had a follow-up exam.

Within an hour, the study found, cannabis eased patient’s pain significantly while also impairing their cognition and making them feel “high” (the higher the THC content, the higher they felt).

But longer term, a different pattern emerged: After two weeks of sustained use, patients reported improvements in pain, sleep quality and cognitive function. Some objective measures of cognitive function, including reaction times, also improved.

“We thought we might see some problems with cognitive function,” said Bryan, noting that both cannabis and chemotherapy have been previously associated with impaired thinking. “But people actually felt like they were thinking more clearly.”

The more people’s pain subsided, the more their cognition seemed to improve.

Those who ingested more CBD, a known anti-inflammatory, reported bigger improvements in sleep quality and pain intensity.

While larger controlled studies are needed, the authors say the findings raise an intriguing possibility: While some forms and dosages of cannabis for pain relief may impair thinking short-term, some regimens might improve cognition in the long run by reducing pain.

Personal experience

Bryan had been studying cancer prevention for years and had just begun studying medicinal cannabis use when, in 2017, her work life and personal health collided with a diagnosis of breast cancer.

After surgery and chemotherapy, she looked to cannabis to help ease her pain.

“The doctors were so supportive of what I wanted to do, but they had no idea what to tell me,” she said. “There was just no data.”

Concerned about using opioids, she created her own custom regimen of more potent THC-heavy products when pain was intense and she could sacrifice some mental sharpness, and milder, CBD-heavy products to keep the pain manageable.

She was not pain-free, but she didn’t take a single opiate during her treatment.

“I was extremely lucky because I had some knowledge about this. Most patients don’t,” she said. 

She hopes her research, and more to come, will help people make better decisions.