A new study has found that cannabinoids may impair rather than improve sleep, with researchers reporting a reduction in REM sleep and total sleep time after a single dose of THC combined with CBD.
The trial – a partnership between the Woolcock Institute of Medical Research and the Lambert Initiative for Cannabinoid Therapeutics – involved 20 participants with a clinical diagnosis of insomnia.
Each participant received a placebo on one night and, on another, an oral dose containing 10mg THC and 200mg CBD.
The single-night study found the cannabinoid treatment reduced total sleep time by 24.5 minutes, largely due to a 33.9-minute decrease in REM sleep – the stage associated with dreaming, emotional processing, and memory consolidation.
The results come as demand continues for cannabis-based treatments for sleep, which account for 12% of approvals under the SAS-B pathway.
Lead researcher Dr Anastasia Suraev said the team wanted to explore the scientific basis behind cannabis’s widely perceived sleep-promoting effects, particularly in light of prescribing trends
“Cannabis is widely promoted in the media as helping sleep – and it’s one of the top three reasons for medicinal cannabis prescriptions in Australia,” she said.
“We wanted to rigorously test that in a controlled environment, with people who had clinician-diagnosed insomnia. We wanted to understand how cannabis affects the sleeping brain.”
The results came as a surprise to researchers.
“We actually thought it would improve their sleep… but the REM suppression and total sleep time reduction took us by surprise,” Suraev said.
Despite enduring more disrupted sleep after the dose, participants did not show signs of next-day impairment. Nine hours after dosing, the researchers observed no decline in alertness, cognitive performance, or simulated driving.
“This is consistent with previous findings from the Lambert Initiative showing that medicinal cannabis, when used appropriately, doesn’t result in prolonged impairment,” Suraev said.
Dr Dev Banerjee, a sleep physician at The New Clinic and former medical director at the Woolcock Institute, praised the research and said it added valuable insights, but noted the difference between trial conditions and clinical practice.
“The latest research may reflect a one-night effect,” he said. “In my practice, I typically start patients on no more than 2mg THC and 25mg CBD at night.”
He said the study should not be interpreted as ruling out cannabis-based medicines for sleep.
“In my opinion, the research does not conclude that medicinal cannabis has no role in treating sleep disorders – far from it,” he said.
“In clinical practice, I’ve found it to be a safer alternative to benzodiazepines for insomnia, and particularly helpful in treating nightmare disorder in PTSD.”
Both Suraev and Banerjee agreed further research was needed to better understand the effects of cannabinoids on sleep.