Insomnia disorder affects around 1 in 10 people worldwide. It can drain energy, affect mood and make everyday life harder. For many people, symptoms last for years, even with treatment.
A study published in Neuropsychopharmacology Reports in 2026 looked at 211 people in the UK who were prescribed medical cannabis for insomnia. The researchers followed their sleep quality, anxiety and quality of life for 2 years. They also recorded side effects. This is the 50th peer-reviewed paper to use data from the UK Medical Cannabis Registry.
Key Takeaways:
- The study. Researchers analysed data from 211 people in the UK Medical Cannabis Registry whose main reason for treatment was insomnia. Each person had been prescribed medical cannabis by a specialist doctor. Their symptoms were tracked over 24 months.
- Sleep quality scores were better at every check-up. On a scale of 0 to 10, average sleep quality rose from 2.46 at the start to 5.14 at 24 months. Scores were highest at 12 months and lower at 24 months.
- Anxiety scores were also lower. Average anxiety scores were lower than at the start at every check-up. Quality of life scores were better at most check-ups, but not at 24 months.
- People with the worst sleep at the start changed the most. This may partly reflect a statistical effect called regression to the mean, explained below.
- Side effects. 17 of 211 people (8.06%) reported at least one side effect. Most were mild or moderate and none were life-threatening. Insomnia, fatigue and dry mouth were the most frequently reported.
- A Registry milestone. This is the 50th peer-reviewed paper to use data from the UK Medical Cannabis Registry.
What it cannot show. There was no comparison group. The study cannot show that medical cannabis caused the changes seen.
What is Insomnia Disorder?
Insomnia disorder is a long-term sleep problem. People have difficulty getting to sleep, staying asleep, or getting good-quality sleep. This happens on at least 3 nights a week for at least 3 months, even when there is enough time and a suitable place to sleep. It also affects how a person feels and functions during the day.
Insomnia often occurs alongside other long-term health conditions, such as anxiety, depression and chronic pain. Each can make the others harder to manage.
Insomnia also has a wider cost. In the UK, it was estimated to cost the economy about £34 billion in 2019. This is due to lost productivity at work, a higher risk of accidents and greater use of health services.
Insomnia can be long-lasting. One study found that around 6 in 10 people with insomnia disorder still had symptoms 5 years later.
How is insomnia treated in the UK?
Treatment depends on how long the insomnia has lasted and what may be causing it. A doctor will usually look for other causes first, such as sleep apnoea, pain, low mood, or medicines that affect sleep.
For long-term insomnia, the National Institute for Health and Care Excellence (NICE) guidance includes:
- Sleep hygiene advice. Practical changes to routines and the bedroom environment that support sleep.
- Cognitive behavioural therapy for insomnia (CBT-I). This is the recommended first treatment for long-term insomnia. It helps people change the thoughts and habits that keep insomnia going. It can be delivered face-to-face or through a digital programme. NICE has recommended one such programme, Sleepio, for use in NHS primary care.
- Sleeping tablets (hypnotics). Z-drugs (such as zopiclone) and benzodiazepines are generally only used for short periods. Longer-term use is linked to dependence and to falls and fractures, especially in older people.
- Melatonin. Prolonged-release melatonin may be used short-term in people aged 55 and over. Evidence on how well melatonin works for insomnia is limited.
- Daridorexant. This is a newer type of medicine called a dual orexin receptor antagonist. NICE recommends it for long-term insomnia when CBT-I has been tried and has not worked, or is not available or suitable. It is currently the only medicine of its type licensed in the UK. Evidence on its long-term effects is still limited.
Can medical cannabis be prescribed for insomnia in the UK?
Yes, in some cases. Since November 2018, specialist doctors on the General Medical Council (GMC) Specialist Register have been able to prescribe medical cannabis. This is usually considered only when licensed treatments have not helped or are not suitable.
Medical cannabis prescribed for insomnia is unlicensed. This means they have not been through the full approval process for this use. NICE has not recommended medical cannabis for insomnia. As a result, they are not routinely available on the NHS for insomnia. Most people who are prescribed it receive treatment privately.
Medical cannabis contains compounds from the cannabis plant called cannabinoids. The two main ones are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Researchers are interested in them because the body’s own endocannabinoid system appears to play a part in regulating the sleep-wake cycle. How this translates to effects in people with insomnia is not yet clear.
What is the UK Medical Cannabis Registry?
The UK Medical Cannabis Registry was set up in December 2019 and is run by Curaleaf Clinic. It is the largest database of its kind in the UK. It collects information on the health and safety of people prescribed medical cannabis. Patients give written consent to take part. The Registry has approval from a research ethics committee.
People in the Registry complete questionnaires about their symptoms online. They do this before starting treatment and then at regular points afterwards.
A milestone: the Registry’s 50th publication
This insomnia study is the 50th peer-reviewed paper to use data from the UK Medical Cannabis Registry. Since the Registry began, its data have been used to study the outcomes and side effects of medical cannabis across many conditions, including chronic pain and anxiety.
Each paper was checked by independent experts before publication. This process is called peer review. Like this one, most Registry studies are observational. They cannot prove that a treatment works. However, they help doctors and researchers understand what happens to patients over time in everyday practice. They can also help shape the design of future clinical trials.
An earlier Registry study on insomnia, published in 2024, followed people for a shorter time. This new study looked at what happened over 2 years.
What did the study look at?
This was an observational study. The researchers analysed information that had already been collected. They did not give treatment as part of a trial, and there was no comparison group.
Who was included?
The study included people in the Registry who:
- had insomnia as their main reason for treatment
- had been prescribed medical cannabis by a specialist doctor
- had completed questionnaires before starting treatment
- had been in the Registry for at least 2 years by January 2025
At the first appointment, doctors recorded each person’s age, sex, weight, job, medical history and other conditions. They also recorded smoking, alcohol use and whether the person had used cannabis before.
What did the researchers measure?
People completed questionnaires at the start and at 1, 3, 6, 12, 18 and 24 months. These measured:
- Sleep quality. The Single-Item Sleep Quality Scale asks people to rate their sleep from 0 (“terrible”) to 10 (“excellent”). This was the main measure.
- Anxiety. The Generalised Anxiety Disorder-7 (GAD-7) questionnaire, scored from 0 to 21.
- Quality of life. The EQ-5D-5L questionnaire, which covers mobility, self-care, usual activities, pain and mood.
- Overall change. The Patient Global Impression of Change, where people rate how much they feel their health has changed.
The team also recorded side effects reported by patients or doctors.
For sleep and anxiety, the researchers used a level of change that patients would be likely to notice. This is called a minimal clinically important difference. For sleep quality, it was a rise of at least 2.6 points. For anxiety, it was a fall of at least 4 points.
Who took part?
Of 34,563 people in the Registry, 211 met the criteria for this study.
- The average age was 42.
- 153 (72.51%) were men and 58 (27.49%) were women.
- 126 (59.72%) were using cannabis before starting treatment, and 45 (21.33%) had used it in the past. 40 (18.96%) had never used cannabis.
- 100 (47.39%) had depression or anxiety as another health condition.
The most common additional reasons for treatment were anxiety (38 people, 18.01%), chronic pain not caused by cancer (12 people, 5.69%) and depression (7 people, 3.32%).
Fewer people completed questionnaires over time. By 24 months, 76 of the 211 people (36.02%) had completed them. The researchers used a statistical method called multiple imputation to estimate the missing scores. This is explained under limitations below.
What did the study find?
Did sleep quality change over time?
Yes. Average sleep quality scores were better than at the start at every check-up. At 24 months, the average score had risen by 2.68 points. This is just above the 2.6-point change that patients would be likely to notice.
Scores were highest at 12 and 18 months. By 24 months they had fallen back, although they were still higher than at the start.
Did anxiety and quality of life change?
Average anxiety scores were lower than at the start at every check-up. At 24 months, 103 of 211 people (48.82%) had a fall in anxiety that patients would be likely to notice.
Average quality of life scores were better than at the start at every check-up except 24 months. At 24 months, scores were about the same as at the start.
These figures include estimated values for people who did not complete questionnaires.
| Measure | At baseline | At 24 months |
| Sleep quality, SQS (0 to 10, higher is better) | 2.46 | 5.14 |
| Anxiety, GAD-7 (0 to 21, lower is better) | 10.41 | 7.36 |
| Quality of life, EQ-5D-5L index (higher is better) | 0.63 | 0.64 |
Were any factors linked to a noticeable improvement?
The researchers looked at which factors were linked to a noticeable improvement at 24 months. They first looked at each factor on its own. They then looked at all factors together, which gives a more reliable picture. Some links did not hold up in the second step.
Sleep quality
- People with the poorest sleep at the start were much more likely to have a noticeable improvement in sleep at 24 months. This link held when other factors were taken into account.
- People with severe anxiety at the start seemed more likely to improve. This link did not hold when other factors were taken into account.
Anxiety
- People with poor sleep at the start seemed more likely to have a noticeable improvement in anxiety. This link did not hold when other factors were taken into account.
- People prescribed higher doses of THC were less likely to have a noticeable improvement in anxiety. This fits with other research suggesting that THC may worsen anxiety at higher doses in some people.
Quality of life
- People with moderate or severe anxiety at the start were more likely to report better quality of life at 24 months. This link held when other factors were taken into account.
Some links were also seen with the form of product prescribed. These were based on small groups and the results were very uncertain.
The authors say that many separate analyses were run. This raises the chance that some links were found by chance. They describe these findings as early signals that need checking in other studies. They cannot be used to predict how any one person will respond.
What side effects were reported?
Seventeen (8.06%) participants reported at least one side effect. Between them, they reported 123 side effects. Of these:
- 59 were mild
- 53 were moderate
- 11 were severe
- None were life-threatening or disabling
The most frequently reported side effects were insomnia (13 reports), fatigue (12), dry mouth (10), sleepiness (9), dizziness (8) and lethargy (8). Headache, a spinning sensation (vertigo), difficulty concentrating, indigestion, memory loss and sudden confusion (delirium) were among the less common reports.
Insomnia was the most common side effect, and 5 of these reports were rated severe. The study did not assess whether side effects were caused by medical cannabis. Reports of insomnia may reflect the underlying condition rather than the medicine.
People aged over 60 (21 people) were more likely to report side effects than younger people.
Why might these results need careful interpretation?
The authors give several reasons why the improvements seen may not all be due to medical cannabis:
- Regression to the mean. People often seek new treatment when symptoms are at their worst. Symptoms can then improve naturally, whatever the treatment. This may explain part of the larger improvement in people with the poorest sleep at the start. Without a comparison group, the two explanations cannot be separated.
- Expectations. Everyone knew they were receiving medical cannabis. People were also paying privately for treatment. Expecting to feel better can affect how people rate their symptoms.
- Who chose treatment. Most people were already using cannabis before treatment. People who had found it helpful in the past may be more likely to seek a prescription.
- Changing doses. The THC doses prescribed tended to rise over the 2 years. The authors say this could reflect the body getting used to THC over time, which is called tolerance. This may help explain why sleep scores were lower at 24 months than at 12 months.
What are the limitations of this study?
The authors point out several important limitations:
- No comparison group. No one received a placebo or standard care instead. A placebo is a dummy treatment with no active ingredient. Without a comparison, it is not possible to say how much of the change was due to medical cannabis.
- Observational design. The study cannot show cause and effect.
- Missing data. Only about 1 in 3 people completed questionnaires at 24 months. The researchers estimated missing scores using multiple imputation. However, people who stopped treatment because it did not help, or because of side effects, may be less likely to have completed questionnaires. This could make results look better than they are.
- Self-reported sleep. Sleep was measured by people’s own ratings, not by sleep tests. It is not possible to say whether the way people actually slept changed, or only how they felt about their sleep.
- Other sleep conditions. The Registry does not record whether people had been tested for sleep apnoea or similar conditions. The authors note that people must have a diagnosis and have tried licensed treatments before medical cannabis can be prescribed.
- A small, selected group. The 211 people were mostly men, mostly already using cannabis, and all treated privately at one clinic. The results may not apply to other groups.
How does this compare with other research?
The results are similar to earlier observational studies. These include the 2024 Registry study on insomnia and a Canadian review of patient records for people with sleep disorders. Both reported improvements in self-reported sleep quality.
All of these studies share the same main weakness. None had a comparison group. Randomised controlled trials of medical cannabis for insomnia have so far been small and short.
What does this study mean, and what does it not mean?
In this group of 211 people in the UK, average sleep quality scores were better at every check-up over 2 years after starting medical cannabis. Average anxiety scores were also lower. The largest changes were seen in people with the poorest sleep at the start. About 1 in 12 people reported side effects. Most were mild or moderate.
The study does not show that medical cannabis works for insomnia. It does not show that they will help any one person. Randomised controlled trials comparing medical cannabis with placebo or standard treatment would be needed to find out their true effect.
Frequently Asked Questions
Can medical cannabis be prescribed for insomnia in the UK?
Yes, in some cases. A specialist doctor on the GMC Specialist Register can prescribe medical cannabis, usually when licensed treatments have not helped or are not suitable. Medical cannabis used for insomnia is unlicensed. NICE has not recommended it for insomnia, so they are not routinely available on the NHS for this purpose.
Does this study show that medical cannabis works for insomnia?
No. This was an observational study with no comparison group. On average, sleep quality and anxiety scores were better at 24 months than at the start. However, the study cannot show that medical cannabis caused these changes. Expectations, regression to the mean and missing data may all have played a part.
How much did sleep quality change in the study?
On a scale of 0 to 10, average sleep quality rose from 2.46 at the start to 5.14 at 24 months. This is a rise of 2.68 points. Scores were highest at 12 months (6.23) and lower by 24 months. These figures include estimated values for people who did not complete questionnaires.
What side effects were reported?
Seventeen of 211 people (8.06%) reported at least one side effect. Of 123 side effects reported, 59 were mild, 53 were moderate and 11 were severe. None were life-threatening. The most frequently reported were insomnia, fatigue and dry mouth. People aged over 60 were more likely to report side effects.
What is the first treatment for long-term insomnia?
NICE guidance recommends cognitive behavioural therapy for insomnia (CBT-I) as the first treatment for long-term insomnia, alongside sleep hygiene advice. CBT-I can be delivered face to face or through a digital programme. Your GP can explain what is available in your area.
How many studies have used data from the UK Medical Cannabis Registry?
This insomnia study is the 50th peer-reviewed paper to use Registry data. Registry studies have covered many conditions, including chronic pain, anxiety and insomnia. Most are observational, so they describe what happens to patients over time but cannot prove that a treatment works.
Who carried out the study?
The study was carried out by researchers at Imperial College London and Curaleaf Clinic. Curaleaf Clinic runs the UK Medical Cannabis Registry. The first author, Aran Koye, is a medical student at Imperial College London. Dr Simon Erridge, Research Director at Curaleaf Clinic, is the corresponding author. All the other authors work for Curaleaf Clinic or Curaleaf International. No funding was reported for the study.
Considering your treatment options?
Insomnia can affect every part of life. If your sleep is not improving, speak to your GP first. They can check for other causes and explain which options may suit you. CBT-I is the recommended first treatment for long-term insomnia. The Sleep Charity also offers advice and support.
Medical cannabis for insomnia is unlicensed in the UK. A specialist doctor may consider them only after a full assessment of your medical history and previous treatments. To find out whether a specialist consultation may be appropriate for you, you can complete Curaleaf Clinic’s online eligibility check. Any treatment decision is made by a specialist doctor on an individual basis.
Thank you to our patients
Research from the UK Medical Cannabis Registry depends on the people who take part. As the Registry reaches its 50th peer-reviewed publication, we would like to thank every patient who has taken the time to share their experience of treatment. Every questionnaire completed adds to what is known about medical cannabis in the UK.
