Real-world evidence plays an important role alongside traditional clinical trials. The UK Medical Cannabis Registry was the first national registry in the UK to systematically collect and analyse clinical data from patients treated with medical cannabis and is now one of the largest datasets of its kind globally.
Important limitations remain across the field, including a shortage of large, high-quality RCTs, significant variation between medical cannabis products, limited long-term safety data, and outstanding questions around cost-effectiveness. The evidence summaries below should be read with these broader limitations in mind.
Explore the latest available evidence for medical cannabis across pain management, psychiatric conditions, and neurological conditions.
Chronic pain is a common reason why patients seek healthcare. Many patients report frustration with existing treatments that offer limited relief or cause significant side effects. Medical cannabis has attracted growing clinical and research interest in this context. Below, we’ll explore the current research on the effects of medical cannabis on pain management.
Chronic non-cancer pain refers to pain that persists or recurs for more than three months and is unrelated to cancer. Affecting approximately one in five adults worldwide, chronic pain includes common conditions such as low back pain and osteoarthritis.
A 2024 meta-analysis by Jeddi et al. found that medical cannabis may offer similar efficacy to opioids in chronic pain with potentially fewer discontinuations due to adverse events.1 Another meta-analysis suggests that non-inhaled medical cannabis is associated with a modelled 10% absolute increase in the proportion of patients achieving a clinically significant response, and a 7% increase in those achieving ≥30% pain reduction, compared with placebo.2
Two recent Phase 3 trials investigated VER-01, a full-spectrum cannabis extract containing Δ9-tetrahydrocannabinol (Δ9-THC), cannabigerol (CBG), and cannabidiol (CBD), in adults with chronic low back pain who had not responded adequately to previous analgesics.
In a placebo-controlled trial of 820 participants, Karst et al. reported a statistically significant reduction in pain intensity, favouring VER-01 over placebo (−1.9 vs −1.4 points on the numeric rating scale; p<0.001).3 A separate head-to-head trial by Meissner et al. compared VER-01 with prolonged-release opioids over 24 weeks in 384 participants.4 The VER-01 group showed a modestly greater reduction in pain intensity (−2.50 vs −2.16 points; p=0.048), with a larger treatment difference observed in patients with a neuropathic pain component or more severe baseline pain.
Neuropathic pain, caused by damage or dysfunction in the nervous system, is often difficult to treat and responds poorly to conventional analgesics. It is a common component of many chronic pain presentations, including low back pain.
Subgroup analyses from the VER-01 trials suggest that patients with a neuropathic pain component may derive greater benefit from medical cannabis. In the placebo-controlled trial, the treatment effect was substantially larger in the neuropathic subgroup (mean difference −1.5 points vs −0.6 overall), with additional improvements on the Neuropathic Pain Symptom Inventory.3 In the opioid comparator trial, a similar pattern was observed, with a trend towards greater benefit for VER-01 in the neuropathic subgroup, though these subgroup comparisons did not consistently reach statistical significance.4
Sleep disturbance affects 60–90% of patients with neuropathic pain and independently contributes to pain severity and disability. In patients with a neuropathic pain component, VER-01 was associated with improvements in sleep quality over 6 months compared with both placebo and opioids.3,4
A recent review from Cochrane reviewed 21 studies involving 2,187 adults with chronic neuropathic pain.5 This review updates a previous version published in 2018. The studies looked at different types of medical cannabis compared to placebo. The review found that the certainty of evidence for most outcomes was low or very low.5 This affects our ability to be confident about the effects of medical cannabis for neuropathic pain based on current research. Most studies included fewer than 50 participants per treatment group, and 14 of the 21 studies were considered at high risk of bias due to their small size. Moreover, many studies lasted only a few weeks.
Some clinical guidelines still consider medical cannabis as a later treatment option for chronic neuropathic pain after established treatments such as certain antidepressants or antiseizure medications have not provided sufficient relief or were not tolerated.
Fibromyalgia is characterised by widespread pain, fatigue, sleep disturbance, and mood symptoms that can significantly affect quality of life. Current therapeutic options demonstrate significant limitations, with licensed pharmacotherapies achieving ≥30% pain reduction in only 40–50% of patients.
Two key RCTs have explored medical cannabis in fibromyalgia. Skrabek et al. evaluated nabilone, a synthetic Δ9-THC analog, in an RCT.6 They reported changes in pain and quality of life compared with placebo, although adverse effects, such as dizziness and drowsiness, were more common in the treatment group. Similarly, Chaves et al. assessed a Δ9-THC-rich cannabis oil in a double-blind RCT and found reductions in fibromyalgia symptom severity and pain scores versus placebo, with acceptable tolerability.7 Whilst promising, both trials were small, and larger, longer-term studies are needed.
Real-world data from the UK Medical Cannabis Registry provide complementary evidence from clinical practice. A prospective cohort of 497 patients followed for up to 18 months showed changes in pain, fibromyalgia symptom severity, and widespread pain measures from baseline.8 Self-reported data also suggest potential improvements in fatigue and anxiety symptoms. However, as with all observational data, these findings should be interpreted cautiously, given the absence of a control group and potential for bias.
Cancer pain affects approximately 45% of patients, and up to 40% experience inadequate relief despite guideline-directed treatment. The evidence for medical cannabis in cancer pain is less well established than for other chronic pain conditions, with conflicting conclusions across systematic reviews.
A 2021 systematic review and network meta-analysis by Wang et al. reported moderate to high certainty evidence that non-inhaled medical cannabis produced small but clinically meaningful changes in pain relief, physical functioning, and sleep quality among chronic pain patients, including cancer pain, compared to placebo.2
Observational data from the UK Medical Cannabis Registry offer longer-term follow-up from clinical practice. This data, gathered from a cohort of 116 patients followed for up to 24 months, indicated that medical cannabis treatment correlated with sustained, patient-reported improvements in pain, anxiety, sleep quality, and overall quality of life. 9 As with other Registry data, the observational design means these findings require confirmation in controlled trials.
Psychiatric conditions affect about 1 in 4 adults globally. Although many patients find relief with approved medications and psychological therapies, others struggle to achieve adequate symptom control. Furthermore, up to 20–30% of patients with depression and anxiety disorders experience treatment resistance, which is charactised by inadequate response to two or more appropriate treatments.
The RCT evidence base for medical cannabis in psychiatric conditions is limited. Much of the existing trial evidence is derived from studies where psychiatric symptoms were secondary outcomes in other conditions, such as chronic pain or multiple sclerosis. However, real-world observational data provide complementary evidence, though with inherent methodological limitations.
Anxiety disorders are among the most prevalent psychiatric conditions, with a global lifetime prevalence estimated at 13–16%. Many patients find effective relief from licensed pharmacotherapies and psychological interventions, particularly cognitive behavioural therapy (CBT). However, for up to 30–40% of patients, first-line treatments don’t offer adequate symptom control.
The evidence base for medical cannabis in anxiety disorders includes a small number of RCTs, primarily using cannabidiol (CBD) isolate, alongside observational data from clinical registries.
Two RCTs examined CBD in individuals with social anxiety disorder. Bergamaschi et al. demonstrated that a single 600 mg dose of CBD reduced subjective anxiety during a simulated public speaking task in 24 treatment-naïve patients with social anxiety disorder compared with placebo.1 In a separate neuroimaging study, Crippa et al. found that a single 400 mg dose of CBD was associated with a subjective reduction in anxiety and altered regional cerebral blood flow in limbic areas in 10 patients with social anxiety disorder.2 Whilst these findings are promising, both studies used single-dose administration in laboratory settings and do not reflect ongoing clinical treatment.
No RCTs have examined Δ9-tetrahydrocannabinol (Δ9-THC)-containing medical cannabis as a primary treatment for anxiety disorders. However, RCTs in chronic pain and multiple sclerosis that measured anxiety as a secondary outcome have reported improvements in anxiety symptoms with nabiximols and other Δ9-THC:CBD preparations.3
The UK Medical Cannabis Registry has published analyses of patients with treatment-resistant generalised anxiety disorder (GAD). Findings indicate that approximately 70% of patients with treatment-resistant GAD reported clinically significant changes at 12 months. Changes in sleep quality and health-related quality of life were also seen.4 However, whilst the observational evidence provides signals of potential efficacy, they cannot establish causality and further research is needed.
First-line treatments for depression, including licensed pharmacotherapies and psychological interventions (particularly cognitive behavioural therapy), are effective for many patients. However, up to 30% of patients are affected by treatment-resistant depression, which is defined as inadequate response to two or more antidepressants of adequate dose and duration.
The evidence base for medical cannabis in depression is limited. No RCTs have been conducted with medical cannabis for major depressive disorder as the primary indication. However, evidence from trials in other conditions provides indirect signals. Some chronic pain RCTs report improvements in mood symptoms as secondary outcomes, although effect sizes are generally modest and inconsistent across studies.3
In the absence of definitive RCT evidence, observational data from clinical registries provide insights into outcomes in real-world practice. In a cohort of 698 patients with treatment-resistant depression, medical cannabis treatment was associated with patient-reported change in depression severity, anxiety, sleep quality, and quality of life that were sustained throughout the follow-up period of 24 months.5 As with all observational data, these findings cannot establish causality due to the absence of placebo controls, selection bias, and attrition. However, the findings may help guide the use of unlicensed or magistral prescription of medical cannabis for patients with treatment-resistant depression.
Insomnia is both a primary disorder and a common symptom across chronic physical and mental health conditions. Current treatments are often inadequate, with high rates of symptom persistence despite therapy. The high persistence rate and limitations of current therapies support exploration of alternative treatment approaches, including medical cannabis. Unfortunately, the evidence base is limited.
A 2021 crossover trial enrolled 23 adults with chronic insomnia. Participants received a cannabis extract containing 10 mg Δ9-THC, 0.5 mg CBD, and 1 mg cannabinol (CBN) for two weeks. Self-reported sleep quality and total sleep time improved compared to placebo. However, polysomnography showed no significant changes in objective sleep parameters.6 The short duration and small sample size limit interpretation.
Real-world data provide a more consistent picture of long-term outcomes. Analysis from the UK Medical Cannabis Registry followed patients prescribed cannabinoids for insomnia for up to 18 months. Self-reported sleep quality changed at all follow-up timepoints compared to baseline.7
Across the broader registry population, 44% of patients reported clinically significant improvement in sleep quality at 24 months. These findings suggest that medical cannabis is associated with sustained benefit in clinical practice, though the observational design and reliance on patient-reported outcomes limit causal inference.8
Many PTSD patients find relief from trauma-focused psychotherapies and pharmacological treatments, including selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs). However, treatment resistance is common: non-response rates reach 50% for psychotherapies and 40% for SSRIs. This unmet need has prompted investigation of novel therapeutic approaches, including medical cannabis.
A systematic review by Black et al. (2019) examined the evidence for medical cannabis in PTSD. The review identified limited studies examining Δ9-THC and CBD combinations. Pharmaceutical preparations of Δ9-THC and CBD demonstrated an advantage over placebo in improving global functioning and nightmare frequency in PTSD patients. Despite these findings, the authors concluded that there is very-low-quality evidence for the effectiveness of medical cannabis for mental health disorders, citing the paucity of good-quality evidence and known risks.3
A small crossover RCT of 10 participants examined nabilone, a synthetic Δ9-THC analogue, in Canadian military personnel with treatment-resistant PTSD-related nightmares for 7 weeks. The findings showedreduced nightmare frequency compared to placebo, and improvements in general well-being and sleep were also reported.9 The study’s limitations include the small sample size and short treatment duration. The focus on a single-centre military population may also limit applicability to broader PTSD populations.
The primary barrier to establishing the efficacy of medical cannabis in PTSD is the limited number of high-quality clinical trials. Several larger RCTs are currently ongoing, and results from these studies will substantially inform the evidence base over the coming years.
Recent observational data from the UK Medical Cannabis Registry provide a detailed examination of long-term outcomes in a cohort of 269 PTSD patients. A 2025 study by Datta et al. reports sustained improvements in PTSD symptoms, anxiety, sleep quality, and health-related quality of life over 18 months.10 However, the observational study design limits causal conclusions.
Patients with neurological disorders, ranging from epilepsy to multiple sclerosis (MS), often experience complex and debilitating symptoms. For many, conventional disease-modifying treatments do not provide adequate symptom control, representing a significant unmet clinical need. Medical cannabis has emerged as a potential therapeutic to address the symptoms of several neurological conditions.
Two medical cannabis products – Epidyolex® and Sativex® (nabiximols) – have received market authorisation for neurological indications, supported by robust randomised controlled trial (RCT) evidence. These licensed therapies represent the strongest level of evidence for medical cannabis in neurology.
Below, we’ll review the current evidence base across key neurological indications.
Epilepsy represents the neurological indication with one of the most developed evidence bases for medical cannabis.
Epidyolex® is an oral solution containing highly purified cannabidiol (CBD), licensed for adjunctive therapy for seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex (TSC) in patients 2 years of age and older. Across available randomised controlled trials, CBD 10mg/kg/day and 20mg/kg/day is associated with a 19.5% and 19.9% greater reduction in seizure frequency compared to placebo, respectively.1
Beyond these specific syndromes, which represent a small proportion of the diverse groups of individuals who are affected by drug-resistant epilepsy (DRE), observational studies and expanded access programmes provide evidence for the broader use of cannabinoids in epilepsy. However, the quality of this evidence differs from the RCT data supporting licensed indications.
Flamini et al. (2023) analysed data from 892 patients with various treatment-resistant epilepsies enrolled in expanded access programmes. Treatment with CBD was associated with a 46–66% reduction in median monthly seizure frequency. Approximately 50% of patients achieved a ≥50% reduction in convulsive seizures, non-convulsive seizures, and epileptic spasms.2 Whilst these findings are promising, the methodological limitations of open-label, uncontrolled data include placebo effects, observer bias, and the absence of a comparator group.
In the paediatric population, the evidence for medical cannabis in the treatment of drug-resistant epilepsy is strongest for Dravet syndrome, Lennox-Gastaut syndrome, and TSC. The evidence supports the use of pharmaceutical-grade CBD (Epidyolex®). Pooled data from RCTs show that CBD at doses of 10 mg/kg/day and 20 mg/kg/day is associated with a 19.5% and 19.9% greater reduction in seizure frequency compared to placebo, respectively. In terms of response rates, patients receiving CBD are 75% more likely to achieve a 50% or greater reduction in seizure frequency compared to placebo. CBD is also associated with a six-fold increase in the likelihood of complete seizure freedom.1
No RCTs have evaluated Δ9-THC-containing cannabis products for epilepsy, but there is limited evidence made up of observational studies and case series on children with treatment-resistant epilepsy. Although the absence of control groups means causation cannot be established, the consistency of findings across multiple cohorts provides a rationale for considering Δ9-THC augmentation when CBD alone is insufficient.
In a multicentre retrospective study of 74 children and adolescents with treatment-resistant epilepsy treated with Δ9-THC-containing oils, 89% of patients reported reductions in seizure frequency, although no standardised outcome measures or comparator group were used. The high response rate may reflect selection bias and placebo or expectation effects.3
A prospective open-label study treated 20 children with Dravet syndrome using a cannabis extract containing CBD 100 mg/mL and Δ9-THC 2 mg/mL (50:1 ratio). The results showed a median motor seizure reduction of 71% with a ≥50% responder rate of 63%.4 However, the small sample size limits generalisability, and the contribution of Δ9-THC versus CBD to the observed effect cannot be determined.
In a prospective case series of 35 children with treatment-resistant epilepsy from the UK Medical Cannabis Registry, 65.7% of those treated with Δ9-THC-containing formulations achieved a ≥50 % reduction in seizure frequency, and 37.1% sustained a ≥90 % reduction in seizure frequency across follow-up.5 The UK Medical Cannabis Registry data establishes short-term tolerability in a real-world setting; however, open-label design and lack of comparator preclude conclusions about causality.
Along with epilepsy, multiple sclerosis (MS) represents one of the most established indications for medical cannabis.
Sativex® (nabiximols) is an oromucosal spray containing Δ9-THC and CBD licensed for MS-related spasticity in multiple jurisdictions, supported by RCT evidence.
A 2022 Cochrane systematic review of five RCTs found that patients receiving nabiximols were 2.5 times more likely to report clinically significant improvement in spasticity (≥30% improvement on the Numerical Rating Scale) compared with placebo.6 Beyond spasticity, the review also evaluated medical cannabis for other MS-related symptoms, including chronic pain, sleep disturbance, and fatigue. Of the pooled data from eight studies, seven demonstrated improvement in MS-related pain with nabiximols or synthetic cannabinoids compared with placebo.6 However, the evidence was rated as low quality due to heterogeneity and risk of bias.
Observational studies support the RCT findings and provide data on longer-term outcomes. The MOVE 2 study followed over 300 patients prescribed nabiximols in routine clinical practice. Over 3–4 months, improvements were observed in spasticity, sleep disturbance, health-related quality of life, and activities of daily living.7
Shah et al. 2025 conducted a prospective case series from the UK Medical Cannabis Registry of 203 patients with MS treated with medical cannabis for up to 24 months. Improvements were observed across multiple domains, including pain, energy, physical function, and health distress, and were sustained throughout follow-up. Improvements were also seen in sleep quality (47% achieving a minimally clinically important difference) and general health-related quality of life.8
Whilst real-world data suggest benefits may extend beyond spasticity, the observational design and the absence of a control group preclude conclusions about causality.
Parkinson’s disease (PD) and Huntington’s disease (HD) are complex, progressive neurodegenerative conditions that affect multiple systems. Currently, there are no available treatments that can modify the course of the disease. Whilst the evidence supporting the use of medical cannabis for the motor symptoms of PD and HD is weak, patients with these conditions frequently suffer from significant non-motor symptoms. There is limited direct evidence that supports the use of medical cannabis for non-motor symptoms such as pain, anxiety, depression, sleep disturbance, and cognitive impairment.
Anxiety affects up to 40% of patients with Parkinson’s disease. In a small randomised, double-blind RCT involving 24 patients with Parkinson’s disease, a single dose of 300 mg of CBD reduced anxiety symptoms and anxiety-exacerbated tremor.9 Broader evidence supports CBD for social anxiety disorder, with RCTs demonstrating anxiolytic effects at doses of 300–600 mg in laboratory settings.10,11
Sleep disorders affect 60–90% of patients with Parkinson’s disease, including insomnia, REM sleep behaviour disorder, and excessive daytime somnolence. One RCT found nabilone improved sleep quality and overall quality of life in patients with Parkinson’s disease.12
Chronic pain affects 40–85% of patients with Parkinson’s disease. Pain types include musculoskeletal, dystonic, central, and neuropathic pain. No RCTs have specifically evaluated cannabinoids for pain in Parkinson’s disease or Huntington’s disease, although evidence supports the potential use of medical cannabis products for general chronic pain and specific subtypes like neuropathic pain.13,14
Migraine is a common and disabling neurological condition, often inadequately controlled with conventional therapies. Emerging evidence for medical cannabis in migraine and headache disorders suggest potential roles in both prevention and acute treatment, although further well-designed RCT studies are necessary.
A systematic review of nine studies reported promising signals for medical cannabis as a preventative agent, with an acceptable safety and tolerability profile.15 However, the included studies were heterogeneous in design, and most were observational or retrospective in nature.
More robust evidence exists for the acute treatment of migraine. A randomised, placebo-controlled trial evaluated vaporised cannabis flower for acute migraine treatment. 67.2% of participants receiving cannabis achieved pain relief at 2 hours compared with 46.6% receiving placebo. Sustained pain freedom was also superior at 24 and 48 hours. No serious adverse events were reported.16 This high-quality RCT evidence supports the use of vaporised cannabis for acute migraine, though replication in larger and more diverse populations is needed.