Medical marijuana may not provide long-term relief of sleep issues in people battling chronic pain, a new study finds, mainly because users may develop a tolerance to the drug.

The finding is important “considering the ageing of the population, the relatively high prevalence of sleep problems in this population, along with the increasing use of medicinal cannabis,” said an Israeli team led by Sharon Sznitman, from the School of Public Health at the University of Haifa.

Various sleep issues

According to the study authors, chronic pain affects between 19% to 37% of adults in the developed world, many who have sleep problems.

Some are turning to medical marijuana for help getting good shut-eye. But how well does it work?

To find out, Sznitman’s group assessed sleep and pain in 128 patients who’d had chronic pain for at least a year. All were over age 50 and about half (66) said they used medical marijuana to help manage their sleep problems.

The type of sleep issues varied: About one in four patients said they always woke up early and weren’t able to get back to sleep; one in five said they always had difficulty falling asleep, and 27% said they woke up during the night.

Of the patients who used marijuana, average duration of use was four years, using an average of 31 grams of the drug per month. Most (69%) said they smoked marijuana, and about one in five used either cannabis oil or vapour.

A downside

The study found that pot users were less likely to wake during the night, but there were no differences between users and nonusers in the time it took them get to sleep or in the frequency of early awakening.

And there seemed to be a downside: The researchers found that more frequent marijuana use was associated with greater difficulty in falling asleep, plus more frequent awakenings during the night.

“This may signal the development of tolerance,” Sznitman’s team wrote.

But the study couldn’t prove cause-and-effect, so other factors might be at play. For example, the authors said that more frequent pot use might simply be an indicator that these people were in more pain or might be depressed/anxious. That might explain these participants’ higher propensity for sleep problems.

One US sleep medicine expert said that for some patients with chronic pain, medical marijuana can offer “some hope”.

The new study is far from conclusive as to the drug’s benefits or risks, said Dr Margarita Oks, attending physician in pulmonary, critical care and sleep medicine at Lenox Hill Hospital in New York City.

Doesn’t reduce cancer pain

“There was no mention of the exclusion of sleep-related disorders, such as obstructive sleep apnoea, that can manifest with insomnia,” she said, “and this may be a huge confounder.”

And Oks said the fact that the study was done in Israel makes a difference, too.

In Israel, “cannabis is legalised and therefore concentrations of THC [the ingredient in marijuana that produces a high] can be objectively and reproducibly measured,” she explained. “In the United States this is not yet the case.”

A second study in the same issue of the journal concluded that cannabinoids (the active chemicals in medical marijuana) do not reduce cancer-related pain. This review pooled the results of five different studies involving more than 1 400 cancer patients. It was led by Dr. Jason Boland of the University of Hull in England.

Both studies were published in the journal BMJ Supportive & Palliative Care.

^{Image credit: iStock}