Researchers have found that cannabinoids may worsen rather than help sleep, with a new study documenting reductions in both REM sleep and total sleep time following a single combined dose of THC and CBD.
The trial – conducted jointly by the Woolcock Institute of Medical Research and the Lambert Initiative for Cannabinoid Therapeutics – recruited 20 people who had received a clinical diagnosis of insomnia.
On separate nights, each participant took either a placebo or an oral dose containing 10mg THC and 200mg CBD.
Across that single night of treatment, participants slept 24.5 minutes less overall, driven primarily by a 33.9-minute drop in REM sleep – the stage linked to dreaming, emotional regulation, and memory consolidation.
The findings come at a time of sustained demand for cannabis-based sleep treatments, which make up 12% of approvals under the SAS-B pathway.
Lead researcher Dr Anastasia Suraev said the team set out to examine whether the widely held belief in cannabis as a sleep aid had a scientific basis, especially given current prescribing patterns.
"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 outcome was not what the team anticipated.
"We actually thought it would improve their sleep… but the REM suppression and total sleep time reduction took us by surprise," Suraev said.
Although participants experienced more disrupted sleep following the dose, they showed no signs of impairment the following day. Nine hours after taking the treatment, the researchers detected no decline in alertness, cognitive function, or simulated driving performance.
"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, welcomed the research as a useful contribution but drew a distinction between the trial's conditions and everyday 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 cautioned against reading the study as evidence that cannabis-based medicines have no place in treating sleep conditions.
"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 that further investigation is needed to fully understand how cannabinoids affect sleep.
