Decoding Cannabis: First placebo-controlled study of cannabis for migraine (THC/CBD)

Decoding Cannabis is our ongoing weekly series where we take real, actionable (and most importantly) recent scientific research on medical cannabis and break all the sometimes overly complicated wording, graphs, and statistics into clear, useful insights for patients. 

In this edition, we are excited to unpack the very first randomised controlled trial on medical cannabis treatment for migraine. This was an in-depth study, and unlike much of the existing medical cannabis research, it actually compared THC, CBD, THC with CBD, and placebo in a carefully controlled design.

The findings were somewhat surprising, but also clear. And they set up the sharpest comparison yet between what THC, CBD, and a combo of both (all tested against a placebo) in migraine treatment means, and where it may fall a little short. 

Can medical cannabis help with migraine relief?

Yes. But as with many other conditions where medical cannabis has already been proven to help, the devil is in the details.

Medical cannabis treatment is never one size fits all. What brings relief for one patient may be less effective, or in some cases more effective, for another. That is why clinical trials like this are truly vital to the progress of medical cannabis treatment understanding, as they show where the strongest benefits are likely and where expectations may need to be tempered.

What this medical cannabis RCT for migraine tested

This study involved 92 participants in a crossover design, where each person treated up to four separate migraine attacks with different options: THC, CBD, THC with CBD, or placebo. 

That structure gave researchers a rare chance to compare how the same patient responded to each treatment.

All treatments were vaporised cannabis flower, standardised to:

• THC (6%)
• CBD (11%)
• THC:CBD mix (a 6% THC and 11% CBD flower used together, reflecting how many patients combine both compounds in real-world treatment)
• Placebo (a cannabis flower with active cannabinoids removed)

What were the results? Let's take a look…

What does research say about CBD for migraine?

CBD alone did not prove to be an effective option for migraine relief in this trial.

Participants inhaled 0.5 grams of 11% CBD flower, which equated to roughly 55 mg of CBD. 

Despite that standardised dose, the outcomes were not encouraging:

• Pain relief at 2 hours: 31% with CBD, compared with 35% on placebo.

• Pain freedom at 2 hours: 16% with CBD, the same as placebo.
• Most bothersome symptom relief: 20% with CBD, again almost identical to placebo.

There was a hint of benefit at one hour, but it faded quite quickly. In practice, CBD alone performed no better than the placebo.

This is not to say that CBD alone is not an effective treatment option for other health concerns. It has already been shown through multiple trials to offer help for patients suffering from a range of health concerns, including anxiety, sleep, and epilepsy. 

The point here is that when it comes to migraines specifically, CBD alone did not outperform a placebo. 

What complicates matters further is that much of what is on offer on the high street does not reflect the kind of CBD used in research. Oils, gummies, and sprays are sold as supplements with little oversight, dosing consistency, and often no medical guidance.

Patients with Releaf, however, have access to medical-grade CBD oils that are subject to the same regulatory scrutiny and oversight as all other prescribed cannabis medicines. These products are consistent, quality-assured, and prescribed with medical supervision, which just can’t be compared to OTC CBD.

How does THC affect migraine symptoms?

This trial paints a clear picture: where CBD fell short, THC on its own delivered partial benefit, but it was the THC:CBD combination that showed the biggest difference. For UK patients, this is key. THC-based treatments are only available through a legal medical cannabis prescription.

With the THC-only treatment option, participants inhaled 0.5 grams of 6% THC flower, equating to around 30 mg of THC. 

At two hours, THC improved pain relief compared with placebo. That said, it did not significantly increase the number of patients who achieved complete pain freedom, nor did it meaningfully improve the “most bothersome symptom” reported (such as light sensitivity, sound sensitivity, or nausea).

THC also came with more noticeable psychoactive effects compared with THC:CBD, something that is important to note and take into account. 

Potential benefits and side effects of THC for migraine

THC offered measurable relief, with many participants reporting positive outcomes. In terms of side effects, some patients reported mild euphoria, sleepiness, or short-term cognitive slowing, even though doses were far lower than those seen in normal recreational use. That meant the psychoactive effects were mild, often fading within 30 minutes or so. No serious adverse events occurred.

The finding is encouraging: even low-dose THC can help, but how did it compare to the combination of THC and CBD?

Does combining THC and CBD work better for migraines?

According to this research yes. The THC:CBD combination clearly outperformed the other treatment options (and the placebo) across all key measures. 

At two hours:

• Pain relief: 67% with THC:CBD, 47% with THC alone, 31% with CBD, 35% with placebo.

• Pain freedom (complete absence of migraine pain): 40% with THC+CBD, 34% with THC, 16% with CBD, 16% with placebo.

• Most bothersome symptom relief (such as sensitivity to light or sound): 61% with THC+CBD, 44% with THC, 20% with CBD, 26% with placebo.
  
  

That paints a very clear picture. A treatment option that contains both THC and CBD was shown to be far more effective in treating an acute migraine attack.

And these benefits were not just short-lived. A significant proportion of patients maintained relief for up to 48 hours after inhalation. This suggests that THC:CBD together offers more than just a quick fix, but actually extends relief in a way that single cannabinoids cannot.

Why THC plus CBD may provide better results

CBD is known to ‘buffer’ the intensity of THC, reducing the risk of unpleasant psychoactive side effects. This balancing act is often described as part of the entourage effect, a term used to explain how cannabinoids and terpenes (the aromatic compounds in cannabis) offer a more well-rounded treatment option - they work better combined than in isolation.

In this trial, the combination produced the clearest evidence of cannabis benefit for migraine, especially for symptoms like light and sound sensitivity.

Is medical cannabis safe and accessible for people with migraines in the UK?

Yes. Medical cannabis for migraines became a legal treatment option in the UK back in November 2018. Yet it is only in the past 18 months or so that it has begun to step out of the margins and into everyday life for patients. 

What the NHS says about medical cannabis for migraine

Access is still mostly through private clinics, with the NHS remaining almost totally reluctant to prescribe beyond three very specific cases: rare forms of epilepsy, multiple sclerosis spasticity, and chemotherapy-related nausea and vomiting. And even for patients battling these issues, very few NHS prescriptions have ever been offered. 

With cannabis-based treatment options being somewhat of a novel and poorly understood approach for many new patients, safety is the natural first concern. Decades of misinformation and heavy stigma towards the plant and its potential use in clinical settings have left a lasting mark. Thankfully, trials like this are starting to shift the picture. By offering hard data rather than hearsay, they are helping both patients and clinicians see medical cannabis as a treatment that can be measured, tested, and trusted.

In this trial, no serious adverse events were reported. The THC:CBD combination not only provided stronger symptom relief, but was also better tolerated than THC alone. 

Because CBD on its own showed a lower level of effectiveness (close to the placebo), effective treatment means THC-based options. These are not available over the counter - the only legal route is a prescription from a private medical cannabis clinic.

Releaf: safe and supported medical cannabis access in the UK

Releaf was founded to bridge the huge gap that plagued the UK medical cannabis industry up until 2023. The goal was clear: fix supply chain issues and make treatment accessible, safe, and supportive for patients across the country. 

That promise is delivered through partnerships with both domestic and international providers, and through the bespoke Patient Dashboard, where everything is managed in one secure place. 

Patients have consultations with our world-class clinical team, ongoing contact with our fully UK-based patient support staff, and full control of prescriptions, ordering, and delivery. The Dashboard was built from the ground up to give patients confidence at every step of their treatment journey and provide them with control over all aspects of their Releaf experience. 

At Releaf, we take digital security extremely seriously. 

Before we even started prescribing, we built the foundations to ensure their data would always be protected. That work began with ISO 27001 and ISO 9001, recognised as the gold standards for data security and quality management. Since then, we have gone further, achieving Cyber Essentials Plus, a UK-backed certification that requires independent testing of our systems to confirm they are resilient against cyber threats.

This commitment to safety extends beyond data. Every patient also receives a medical cannabis card, offering simple proof of prescription that can be carried anywhere.

FAQs

Does cannabis cure headaches?

No. Cannabis does not cure headaches or migraines, as it will not cure the condition to the point that the patient never has to deal with a migraine again. What it can do is reduce the intensity and frequency of symptoms. In this trial, THC and the THC:CBD combination offered meaningful relief, but treatment is about management, not a cure.

Can medical cannabis help with chronic migraines?

Yes, especially when conventional treatments have failed. The trial showed that THC:CBD delivered the strongest benefit, with some patients experiencing relief for up to 48 hours. This suggests medical cannabis is an option that should be seriously considered for those living with recurring headaches and/or chronic migraines.

Does medical cannabis work for headaches and migraine compared to a placebo?

Yes. The THC:CBD combination significantly outperformed placebo for pain relief, pain freedom, and symptom control. THC alone also showed some benefit, while CBD on its own did not perform better than placebo.

Could medical cannabis be the next step in your migraine care?

For far to many people dealing with the underlying fear of having another migraine, conventional medicines either fall short or bring unwelcome side effects. This new clinical trial shows that cannabis-based treatments are more than theory: they can offer real-world relief without serious safety concerns.

The challenge for UK patients is not whether cannabis works, but how to access it legally and safely. The NHS does not prescribe cannabis for migraine, which means private clinics remain the only route to treatment.

That is exactly why Releaf exists. To give UK patients the access they not only need, but deserve, to a proven treatment option that can help - not just with headaches and migraines, but with a huge range of other conditions and health concerns

CBD alone was not effective in this trial. If you are considering whether THC-based medical cannabis might be suitable for managing migraine, start with Releaf’s free medical cannabis eligibility checker. It takes less than 20 seconds and could be your first step toward safe, legal access to treatment in the UK and a better quality of life. 

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