New study shows cannabis can ease 'chemo brain'. New research from the University of Colorado at Boulder suggests that cancer patients who use marijuana to manage their symptoms not only experience pain relief and improved sleep quality, but also enjoy another unexpected benefit: they seem to be able to think more clearly after a few weeks of continuous use.

"It's hard to think when you're in a lot of pain," said senior author Angela Bryan, a professor of psychology and neuroscience at the University of Colorado Boulder and a cancer survivor. "We've found that when patients' pain levels go down after using cannabis for a period of time, their cognitive abilities improve as well."

The small but groundbreaking study, recently published in the journal Medical Exploration, is one of the first to assess how cannabis purchased over the counter at a dispensary (as opposed to government-supplied or synthetic cannabis) affects cancer symptoms or chemotherapy side effects.

The study also explored the various products used by cancer patients, as it is legal in most states.

It showed that as many as 40 per cent of American cancer patients use cannabis, but only a third of doctors are willing to advise them about it.

Studying it is complicated by the fact that federal law prohibits university researchers from possessing or distributing marijuana for research unless it is government-issued or pharmaceutical-grade. As a result, most studies focus only on prescription products such as cannabilon or dronabinol (often used to treat nausea) or government cannabis strains, which tend to be less potent and lack a wide range of over-the-counter medications.

The research group took a different approach.

Bryan worked with oncologists at the CU Anschutz Medical Campus to observe 25 cancer patients who had been using cannabis for more than two weeks.

After a baseline appointment to assess their pain levels, sleep patterns and cognition, they were asked to purchase an edible product of their choice from the dispensary. The selection was varied, covering 18 brands, including chocolates, gummies, tinctures, pills and baked goods, and contained varying proportions of THC (tetrahydrocannabinol) and CBD (cannabidiol) in varying potencies.

Brian says, "What this tells us is that people are willing to try anything they think will work, but there's not a lot of data to guide them on what works best."

To study severe effects, researchers drove a "mobile lab" (a Dodge sprinter van, sometimes called a "cannavan") to each patient's home one day. Participants were physically and cognitively assessed in the van and then retested in the van after using cannabis at home.

After two weeks of continuous use at a frequency of their choosing, they were followed up.

The study found that within an hour, cannabis significantly relieved the patients' pain, but also impaired their cognition, making them feel "high" (the higher the THC content, the higher they felt). In the long run, however, a different pattern emerged: after two weeks of continued use, patients reported improvements in pain, sleep quality, and cognitive function. Some objective indicators of cognitive function (including reaction time) also improved.

Brian said, "We thought we might find some cognitive functioning issues." He noted that marijuana and chemotherapy have both been previously linked to impaired thinking. "But people actually felt like they were thinking more clearly."

The more pain relief people had, the more their cognitive abilities seemed to improve. Those who consumed more CBD reported greater improvements in sleep quality and pain intensity. Although larger controlled studies are needed, the authors say the findings raise an interesting possibility: while some forms and doses of cannabis used for pain relief may impair thinking in the short term, certain therapies may improve cognition in the long term by reducing pain.

Brianne has been researching cancer prevention for many years, and in 2017, when her work life and personal health conflicted with a diagnosis of breast cancer, she had just begun researching the use of medicinal cannabis. After surgery and chemotherapy, she sought cannabis for pain relief. "The doctors were very supportive of what I wanted to do, but they didn't know what to tell me," she said. "There was just no data."

Concerned about opioid use, she created her own customised programme using the more effective THC heavy products when the pain was intense, and she was able to sacrifice some of her mental acuity and use the gentler CBD heavy products for pain control. She was not pain-free, but she did not take any opioids during treatment. "I was very lucky because I had some knowledge about it. Most patients don't," she says. She hopes her research and more research in the future will help people make better decisions.