Insomnia is a common sleep disorder characterised by sleep disturbance that is linked to daytime impairment. Insomnia disorder is diagnosed when patients experience at least three days per week of sleep disturbance for at least three months. Around one in ten adults lives with insomnia disorder. It can raise the risk of other health problems, including depression, anxiety, and cardiovascular disease.
Despite this, current therapies for the treatment of insomnia are often limited. While cognitive behavioural therapy (CBT) demonstrates efficacy in improving insomnia symptoms, it may be subject to accessibility and scalability issues. On the other hand, pharmacotherapies have limited tolerability and may be associated with safety risks and limited tolerability for many patients.
Medical Cannabis for Insomnia
Medical cannabis is now legal in the UK, and cannabis-based medicinal products (CBMPs) can be prescribed for a wide range of conditions, including insomnia disorder. However, clinical evidence of their efficacy remains limited, with very few randomised controlled trials (RCTs) having been conducted in this area.
Most insomnia studies have focused on Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). However, cannabinol (CBN), an oxidative by-product of THC, has been the subject of increased research for sleep-promoting properties in recent years. However, no objective scientific evidence currently supports the use of CBN as a treatment for insomnia.
To build on this evidence, researchers conducted a randomised controlled trial, published in the Journal of Sleep Research in 2026, to evaluate the outcomes of patients prescribed CBN for insomnia disorder.
What Did the New Trial Involve?
Researchers at the Woolcock Institute of Medical Research in Sydney, Australia, conducted a randomised, double-blind, placebo-controlled trial. This is one of the most rigorous types of clinical study.
Twenty adults aged 25 to 65 with a doctor-confirmed diagnosis of insomnia disorder took part. Each participant spent three separate nights in a sleep laboratory. On one night they received a 30 mg dose of CBN. On another night they received a 300 mg dose of CBN. On the third night they received a placebo (a dummy treatment with no active ingredient). Neither the participants nor the research staff knew which treatment was given on which night.
The researchers measured sleep using polysomnography — a detailed overnight test that monitors brain activity, eye movements, and muscle activity. This gave them objective data on sleep quality, rather than relying solely on how participants said they felt.
What Did the Researchers Find?
The main outcome: time awake during the night
The study’s primary goal was to measure how long participants spent awake after first falling asleep. This utilises a measure known as wake after sleep onset (WASO). Neither dose of CBN produced a statistically significant change in WASO compared to placebo. This means the trial did not demonstrate that CBN reduces the main measure of sleep disturbance tested.
Secondary findings with 300 mg CBN
While the primary outcome was not met, the higher dose showed some changes in secondary and other outcomes that may be of interest for future research:
- Participants fell asleep around 7 minutes faster on average, compared to placebo. This is a similar magnitude to other medicines studied for sleep onset.
- Participants spent a slightly higher proportion of the night in a sleep stage called N2 (a lighter stage of sleep), compared to placebo.
- Participants reported better sleep quality on the morning after taking CBN, using two validated questionnaires.
- There were fewer brief arousals (micro-wakings) during sleep.
- Next-day mood appeared to improve with both doses, compared to placebo.
What about the lower dose?
The 30 mg dose produced fewer notable changes overall. Some differences in brain wave activity during sleep were observed, but the dose did not significantly affect sleep quality scores or the time taken to fall asleep.
Were There Any Side Effects?
No serious side effects were reported. No participants left the study early because of adverse effects. A total of 246 mild side effects were recorded across all three treatment arms, including the placebo group, which is typical in this kind of sleep study. The most commonly reported experiences included:
- Fatigue
- Drowsiness
- Lethargy
- Dry mouth
- Dizziness
- Nausea
The 300 mg dose was associated with mild subjective drug effects, meaning some participants noticed they had taken something. However, the researchers note these effects were much milder than those typically reported with THC, and comparable to responses seen with low doses of alcohol in other studies.
The study also included a simulated driving test the morning after. CBN did not affect the measure most sensitive to driving impairment (lane weaving). However, the higher dose did produce some subtle changes in how participants maintained distance from a vehicle ahead, which warrants further attention in longer-term research.
What Are the Limitations of This Study?
It is important to read these findings in context. This was an early-stage, proof-of-concept study with several important limitations:
- Small sample: Only 20 participants took part. Results from small studies can be affected by chance and may not reflect the wider population.
- Single night only: Each treatment was tested over a single night in a laboratory. Insomnia often varies from night to night, and this design may not capture long-term effects.
- Laboratory setting: Sleep in a laboratory may differ from sleep at home, which could affect the results.
- Mostly female participants: 17 of the 20 participants were women. This means the findings may not apply equally to all people with insomnia.
- Healthy participants only: People with other health conditions or taking other medicines were excluded, so results may not generalise to people with more complex needs.
- Single doses only: The study used single doses. The effects of repeated, nightly use are unknown.
The authors are clear that this trial does not provide direct evidence that CBN is effective for insomnia in routine clinical care. They call for larger, longer studies to build on these findings.
What Does This Mean for Patients?
This trial is the first of its kind to examine CBN’s effects on objectively measured sleep in people with clinically diagnosed insomnia. While it did not demonstrate a significant effect on the main outcome measured, it does suggest that some aspects of sleep and sleep quality may be worth exploring further in larger studies.
CBN is not currently an established or approved treatment for insomnia in the UK. As with all aspects of medical cannabis prescribing, any decisions about whether a cannabis-based medicinal product may be suitable for a particular patient must be made by a specialist clinician, taking into account the individual’s full medical history and circumstances.
Medical cannabis is typically considered when other treatments have not worked well enough. It is not a first-line treatment for insomnia.
