Many people use cannabis products hoping to get a better night’s sleep. In fact, poor sleep is one of the top reasons people turn to cannabis, especially in places where medicinal marijuana is legally available. But a new study by researchers from Macquarie University and the University of Sydney shows that cannabis might actually reduce sleep time, at least in people with insomnia.
The findings, published this week in the Journal of Sleep Research, suggest that a single dose of medicinal cannabis may decrease total sleep time and reduce REM (Rapid Eye Movement) sleep, the sleep stage linked to dreaming and emotional processing.
What was the study about?
This small pilot study involved 20 adults, all of whom had been clinically diagnosed with insomnia disorder. This means they had trouble falling asleep, staying asleep, or both, and their sleep problems were affecting their daily life, whether at work, in relationships, or with their mental health.
Before the study began, participants underwent medical screening and an overnight sleep test to make sure their symptoms weren’t caused by something else, like sleep apnea. Each person then spent two nights at a sleep lab, with a week between visits. On one of the nights, they were given a placebo (a dummy treatment). On the other night, they were given a single oral dose of medical cannabis oil that contained:
- 10 mg of THC – the compound in cannabis that makes people feel “high”
- 200 mg of CBD – a non-intoxicating compound often used for relaxation and pain relief
The order of treatment was random, and participants didn’t know which night they received the real cannabis oil.
How was sleep measured?
During each sleep session, participants wore a high-tech cap with 256 sensors (called a high-density EEG), which recorded brain activity throughout the night. This allowed the researchers to track different stages of sleep, including REM sleep, which is important for emotional health, learning, and memory.
After waking up, participants took part in several tests to check their alertness, attention, and cognitive performance. These included a driving simulation and a sleepiness test in a quiet, dimly lit room. They repeated this test four times during the day while wearing the same EEG cap.
What did the researchers find?
The results were unexpected. Instead of helping people sleep longer, the cannabis product reduced total sleep time by about 24.5 minutes on average. Even more significantly, it reduced REM sleep by about 33.9 minutes and made it take longer for participants to enter REM sleep.
The treatment also didn’t seem to help people stay asleep longer through the night.
Surprisingly, though, participants didn’t feel like they had slept worse. Even though their brain activity showed poorer sleep quality, most said they didn’t notice much difference in how they felt. Some even said they felt a little sleepier the next morning—but when tested, their alertness, memory, and driving ability were not affected.
So, is cannabis bad for sleep?
Not necessarily—but this study challenges the common belief that cannabis always helps people sleep better. According to the researchers, this disconnect between how people feel they slept and what actually happens in the brain is important.
More importantly, this study only looked at a single dose, taken one time. We still don’t know how cannabis affects sleep when taken regularly over weeks or months. Does the body get used to it? Could the negative effects on sleep get worse, or might the body adjust?
Right now, we don’t have enough evidence to say for sure.
Why this research matters
The researchers say their findings highlight the need for more long-term studies with larger groups of people. Medicinal cannabis is becoming more popular, but the science is still catching up.
In a separate review, the team looked at 21 recent studies on the use of cannabinoids for various sleep disorders, such as insomnia, sleep apnea, restless legs syndrome, and REM sleep behaviour disorder. They found that while many people are using cannabis products, there’s still not enough solid evidence to recommend them as safe, effective sleep treatments.
While cannabis products may feel like they help people fall asleep, this new study suggests that they might actually reduce important parts of sleep, like REM. The long-term effects of using medicinal cannabis for sleep are still unknown, especially when taken every night.
For now, doctors and patients should be cautious. Cannabis might be useful for some, but it’s not a one-size-fits-all solution.
