Migraine is a chronic neurological condition characterised by several symptoms, including severe headache, sensitivity to light, nausea, and visual auras.
A new study published in Brain and Behavior has looked at two years of data from adults with migraine in the UK who were prescribed medical cannabis after other treatments had not helped them enough. This article explains what the researchers did, what they found, and importantly, what the findings cannot tell us.
What is migraine, and why is new research needed?
Migraine is a long-term neurological condition. Attacks can cause severe headache, sensitivity to light and sound, feeling sick, and visual changes known as aura. Attacks often last between 4 and 72 hours, and around half of people with migraine have attacks on two or more days each month.
Migraine is the second leading cause of disability in people aged 15 to 49 worldwide. It can have a big effect on work, relationships, sleep and overall well-being.
Licensed medicines, lifestyle changes and other therapies help many people. But some patients continue to have frequent or severe attacks despite trying several treatments. For a small number of these patients in the UK, medical cannabis may be considered under specialist care once licensed treatments have been tried without enough benefit.
What is the UK Medical Cannabis Registry?
The UK Medical Cannabis Registry (UKMCR) was set up by Curaleaf Clinic in 2019. It collects real-world information from patients across the UK who have been prescribed cannabis-based medicinal products for a range of health conditions. The goal is to build a clearer picture of what happens over time: how symptoms change, how well the medicines are tolerated, and what side effects are reported.
The research discussed here was carried out by a team that includes Curaleaf Clinic staff.
What did the study look at?
The research team looked at 203 adults who had migraine as their main reason for treatment, and who had been enrolled in the registry for at least two years. Each person had tried and not got enough benefit from licensed migraine treatments before starting medical cannabis.
Patients filled in questionnaires before starting treatment (baseline) and then at 1, 3, 6, 12, 18 and 24 months. Any side effects were recorded during the study.
Which questionnaires were used?
The researchers used a mix of migraine-specific and general health questionnaires:
- Headache Impact Test-6 (HIT-6) — how much headaches affect daily life.
- Migraine Disability Assessment Test (MIDAS) — how many days migraine stops normal activity.
- EQ-5D-5L — a widely used measure of health-related quality of life, covering mobility, self-care, usual activities, pain/discomfort and anxiety/depression.
- Generalised Anxiety Disorder-7 (GAD-7) — a measure of anxiety symptoms.
- Single Item Sleep Quality Scale (SQS) — a simple rating of sleep quality.
- Patient Global Impression of Change (PGIC) — the patient’s own view of how much their condition has changed.
What did the findings show?
The study reported changes in average scores across the group. None of these results mean a medicine worked for any one person — they are group-level observations without a comparison group.
Did headache scores change?
Average HIT-6 scores decreased at every follow-up point compared with baseline. Average MIDAS scores decreased at 1, 3, 6 and 12 months, but the changes at 18 and 24 months were not statistically significant. The authors suggest this could reflect several things, including natural variation in migraine over time or a possible tolerance effect to treatment.
What about quality of life?
Average EQ-5D-5L index scores increased at every time point, suggesting a change in overall perceived quality of life at the group level. Pain/discomfort scores changed at every time point. Anxiety/depression scores improved up to 12 months but not at 18 and 24 months.
Did sleep and anxiety scores change?
Average GAD-7 (anxiety) scores and SQS (sleep quality) scores improved at every time point. Around 39% of patients reached a meaningful change threshold on the GAD-7 at 24 months, and around 47% on the SQS.
What side effects were reported?
Thirty-one patients (15.27% of the group) reported a total of 249 side effects over the two years. Of these, 44.18% were classed as mild, 31.73% as moderate and 26.91% as severe. Three side effects (1.20%) were graded as life-threatening or disabling: somnolence (excessive sleepiness), delirium and confusion.
The most commonly reported side effects were headache, dry mouth, impaired concentration, fatigue, nausea and lethargy. The authors note that headache appearing as a side effect in a migraine population is difficult to interpret, since patients in this group experience headaches as part of their underlying condition.
What do these numbers actually mean?
A change in an average score across a group is not the same as a treatment “working.” Some patients will improve, some will stay the same, and some will get worse. Without a control group of similar patients who did not receive the treatment, we cannot know how much of the change is due to the medicine itself. Placebo response, regression to the mean and the natural ups and downs of migraine can all look like improvement.
How does it compare with previous research?
These findings build on previous research, which also used UKMCR data to assess the potential of CBMPs in headache disorders over 6 months. Like this previous study, the current analysis observed changes in PROMs up to 6 months, but also highlights a sustained improvement over 24 months. However, it is important to note a downward trend in patients achieving MCID in the HIT-6 and MIDAS over time.
How should these findings be interpreted?
The authors are clear that this type of study cannot prove that medical cannabis caused any of the changes reported. The main reasons for caution are:
- No control group or blinding. Without a comparison group, improvements could reflect placebo effect, the natural ups and downs of migraine, regression to the mean, or other changes in a patient’s life.
- High dropout rate. By 24 months, questionnaire data were only available for around 120 of the 203 patients. Patients who dropped out may have had different experiences from those who stayed in the study.
- Selection bias. Participants were paying patients of a private clinic, most of whom had used cannabis before. This group does not reflect the wider UK migraine population.
- Over-representation of men. Migraine is more common in women, but 56% of this group were men. Results may therefore not be generalisable.
- Self-reported outcomes. All the scores come from patient questionnaires, which can be influenced by expectation, memory and current mood.
- Possible tolerance signal. Fewer patients reached a meaningful improvement on migraine-specific scores (HIT-6 and MIDAS) at later time points, despite higher prescribed doses.
What does this mean for people living with migraine in the UK?
Migraine care in the UK has many starting points. These include lifestyle and trigger management, over-the-counter pain relief, prescribed acute treatments, preventive medicines, newer injectable therapies, neuromodulation devices, and psychological support such as cognitive behavioural therapy. For most people, a combination of these approaches guided by a GP or neurologist will be appropriate.
Medical cannabis is not a first-line option. Under current UK guidance, it may be considered only by a specialist doctor, and only when licensed treatments have been tried and have not provided enough benefit. Eligibility is assessed on an individual basis, taking into account a patient’s full medical history and other medicines.
Research like the study described here adds to the wider picture, but it does not change the standard approach. Larger, better-controlled trials are needed before firm conclusions can be drawn for population-level treatment on the NHS.
