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Medical Cannabis and Mental Health: Evidence, Clinical Judgment and Responsible Prescribing

May 19, 2026 | IN INFORMATION | BY Kate Thorpe
Medical Cannabis and Mental Health: Evidence, Clinical Judgment and Responsible Prescribing

Medical cannabis should be discussed in mental health with the same seriousness as any other developing area of medicine: neither romanticised nor dismissed. Recent debate has rightly drawn attention to the need for better evidence, clearer standards and stronger clinical governance. But the conclusion should not be that cannabis-based medicinal products have no place in mental health care.

The more accurate conclusion is that the evidence is uneven across indications, that the literature is still developing, and that prescribing must be careful, specialist-led and evidence-informed. That position is entirely consistent with the Medical Cannabis Clinicians Society’s updated Good Practice Guide, which states that CBMPs can be prescribed safely where there is appropriate assessment, oversight and follow-up, and that prescribing should remain structured, accountable and aligned with wider professional standards.1

Medical cannabis is not a speculative field

Outside psychiatry, the therapeutic role of medical cannabis is already established and widening. NICE guidance already addresses cannabis-based medicines in severe treatment-resistant epilepsy, spasticity in multiple sclerosis, chronic pain and chemotherapy-induced nausea and vomiting.2

The evidence base is still developing, but it already includes signals that are clinically relevant. In ADHD, the EMA-C pilot RCT of Sativex in 30 adults reported nominal improvements in hyperactivity/impulsivity and inhibition. More recently, a phase 3 randomised placebo-controlled trial of a full-spectrum cannabis extract in chronic low back pain met its primary endpoint and showed statistically significant improvements in pain, sleep and physical function versus placebo.3 

There is also a clear mechanistic rationale for considering cannabinoids in psychiatric practice. The endocannabinoid system is not simply involved in pain or appetite; it is a neuromodulatory system with recognised roles in emotional processing, stress response, fear regulation, synaptic plasticity and neuroplasticity. A 2025 review13 specifically examined the contribution of the endocannabinoid system to the neurobiology of emotions, describing its relevance to brain circuits involved in mood, anxiety, stress and adaptive emotional regulation. 

Mental health should therefore not be discussed as though cannabis were a wholly speculative therapy; it sits within a broader clinical field in which evidence is already stronger for some conditions than for others.

The MCCS Good Practice Guide reflects this reality. It identifies anxiety and related disorders, sleep disorders and symptom clusters such as pain, sleep disturbance and anxiety among the common indications encountered in practice, while explicitly acknowledging that the evidence base varies between conditions.1 Some areas rely more heavily on established evidence; others depend more on emerging evidence, real-world data and clinical experience. That is not a weakness unique to cannabis medicine. It is a familiar feature of many areas of specialist prescribing, particularly where patients present with complex, overlapping symptoms and have already failed, not tolerated, or derived insufficient benefit from conventional options.

Evidence gaps are not the same as evidence of no effect

The recent 2026 Lancet Psychiatry review is an important contribution and should be taken seriously. It examined 54 randomised trials involving 2,477 participants and concluded that there was little RCT evidence of efficacy for several mental and substance use disorders. It also found no randomised controlled trial evidence for depression,4 and a 202613 review found that controlled evidence for cannabinoids in OCD remains very limited. That matters. But it does not follow that cannabinoids have been shown to be ineffective in depression or OCD, or that all psychiatric use is unjustified. In depression in particular, the review highlights an evidence gap, not evidence of no effect. In other words, absence of RCT evidence is not the same as proof of therapeutic futility.

This distinction matters because clinicians do not treat meta-analyses in the abstract; they treat patients in front of them. In real-world practice, many patients seeking CBMPs for mental health symptoms have chronic anxiety, trauma-related symptoms, poor sleep, autonomic hyperarousal, pain, and marked impairment in quality of life. They have often already tried multiple licensed treatments, psychological interventions, or both. The MCCS framework is clear that CBMPs are not first-line treatments and that conventional evidence-based options should normally have been appropriately explored first. But it is equally clear that prescribing is ultimately based on individual clinical judgment, patient need, risk profile and informed consent.1

Those real-world data are now too substantial to ignore. Project Twenty21 has reported consistent improvements in symptoms, general health and quality of life in large cohorts of UK patients, and its sleep analysis found clinically significant improvements sustained for up to 12 months together with reduced use of sleep medication.5,8 The UK Medical Cannabis Registry has shown similar signals in generalised anxiety disorder and PTSD, with improvements in anxiety, sleep and health-related quality of life and with most reported adverse events mild or moderate.6,9 Most strikingly for current debate, registry data in depression now extend to 24 months and show sustained improvement in depression scores, anxiety, sleep and quality of life in selected patients.10 These studies do not prove causation. They do, however, show that the lived clinical experience of benefit is not fanciful and should not be dismissed as irrelevant simply because it comes from observational data.5,6,8-10 

International registry data point in the same direction. A large Australian longitudinal cohort of 3,961 cannabis-naive patients prescribed oral medicinal cannabis reported sustained improvements across multiple validated outcomes over two years and concluded that treatment was safe and well tolerated, while explicitly acknowledging the limits of real-world data for causal inference. This is the correct balance: neither overstatement nor dismissal. Real-world evidence cannot settle every question, but it is highly informative on tolerability, safety, prescribing patterns and patient-reported outcomes in routine care.7

Risk must be managed, not denied

A supportive clinical position does not mean an uncritical one. The MCCS guidance is explicit that psychiatric prescribing requires particular care. It recommends structured psychiatric risk assessment, review of medical records, consideration of risk, and closer monitoring in higher-risk cases. It also emphasises that THC-containing CBMPs require additional caution in patients with a history of psychosis or schizophrenia, while noting that CBD-dominant products may be considered in selected cases because of their non-intoxicating and potentially antipsychotic profile.1 The point is not to deny risk, but to manage it properly.

That is why the most credible position for a clinician-led society is neither overclaiming nor retreat. Medical cannabis has a legitimate place in mental health care for selected patients. The evidence is stronger for some conditions and symptom domains than for others. For depression, the central problem is not that cannabinoids have been disproven, but that high-quality randomised trials are still lacking while observational evidence continues to grow.4 The appropriate response is therefore clear: prescribe carefully, select patients properly, document honestly, monitor closely, and continue to build the evidence base. That is not special pleading for cannabis – it is simply what responsible evidence-based medicine looks like in a developing field.

Supporting clinicians to prescribe safely in psychiatric practice

For clinicians who want to build confidence in this area, the Society is also developing a dedicated Psychiatry Evidence Base, bringing together the current research, clinical evidence and real-world data relevant to mental health prescribing. This will sit alongside the Society’s wider evidence base series and support clinicians in making careful, informed decisions in this complex area of practice.

The Society has also launched a new online training course for healthcare professionals: Medical Cannabis and Mental Health: Evidence, Clinical Judgment and Responsible Prescribing.

Written by Dr Luisa Searle, Consultant Psychiatrist, the course provides a practical, clinically focused introduction to the use of cannabis-based medicinal products in psychiatric practice. It explores how CBPMs may be considered in patients with anxiety disorders, obsessive-compulsive disorder, post-traumatic stress disorder and depression, while making clear that these treatments are not first-line options and require careful patient selection, risk assessment, monitoring and documentation.

The course covers the role of CBD and THC, the relationship between the endocannabinoid system and psychiatric symptoms, contraindications and cautions, including psychosis vulnerability, mood destabilisation, substance use disorder, suicidality, drug interactions and the risks associated with higher THC exposure. Through condition-specific teaching and practical case studies, learners will gain a clearer understanding of how CBPMs may be used as adjunctive treatment within a broader care plan, while maintaining good governance, shared care communication and professional accountability.

Take the course

Please note, CPD accreditation is pending. Learners will receive a certificate on completion, with an updated certificate issued once CPD accreditation is confirmed.

References

  1. Medical Cannabis Clinicians Society. Good Practice Guide for Prescribers of CBMPs. Version 4. London: MCCS; 2026 Apr
  2. National Institute for Health and Care Excellence. Cannabis-based medicinal products. NICE guideline NG144. London: NICE; 2019 [updated 2021].
  3. Karst M, Meissner W, Sator S, Keßler J, Schoder V, Häuser W, et al. Full-spectrum extract from Cannabis sativa DKJ127 for chronic low back pain: a phase 3 randomized placebo-controlled trial. Nat Med. 2025;31:4189-4196.
  4. Wilson J, Dobson O, Langcake A, Mishra P, Bryant Z, Leung J, et al. The efficacy and safety of cannabinoids for the treatment of mental disorders and substance use disorders: a systematic review and meta-analysis. Lancet Psychiatry. 2026;13(4):304-315.
  5. Schlag AK, O’Sullivan SE, Zafar RR, Nutt DJ. Characteristics of patients and patterns of cannabis-based medicinal product use in Project Twenty21: an observational study of 2833 patients in the UK. J Psychopharmacol. 2023;37(7):730-739.
  6. Warner-Levy J, Erridge S, Clarke E, McLachlan K, Coomber R, Asghar M, et al. UK Medical Cannabis Registry: a cohort study of patients prescribed cannabis-based oils and dried flower for generalised anxiety disorder. Expert Rev Neurother. 2024;24(12):1193-1202.
  7. Vickery AW, Roth S, Ernenwein T, Kennedy J, Washer P. A large Australian longitudinal cohort registry demonstrates sustained safety and efficacy of oral medicinal cannabis for at least two years. PLoS One. 2022;17(11):e0272241.
  8. Lynskey MT, Athanasiou-Fragkouli A, Thurgur H, Schlag AK, Nutt DJ. Changes in sleep quality among patients prescribed medicinal cannabis: real-world evidence from Project Twenty21. Drug Sci Policy Law. 2025;11:20503245251362491.
  9. Datta A, Erridge S, Warner-Levy J, Clarke E, McLachlan K, Coomber R, et al. UK medical cannabis registry: an updated clinical outcomes analysis of patients with post-traumatic stress disorder. Expert Rev Neurother. 2025;25(5):599-607.
  10. Lillywhite E, et al. UK Medical Cannabis Registry: a two-year case series of clinical outcomes in depression. J Affect Disord. 2026;399:121130.
  11. Pontes LR, Ribeiro S. Contributions of the endocannabinoid system to the neurobiology of emotions: Advances and perspectives. Progress in Brain Research. 2025;296:65-93. doi:10.1016/bs.pbr.2025.08.001. 
  12. Cooper RE, Williams E, Seegobin S, Tye C, Kuntsi J, Asherson P. Cannabinoids in attention-deficit/hyperactivity disorder: A randomised-controlled trial. European Neuropsychopharmacology. 2017;27(8):795-808. doi:10.1016/j.euroneuro.2017.05.005. 
  13. Van Ameringen M, Patel V, Patterson B, Hopkinson P, Rahat M. New treatments for OCD? Evidence for cannabinoids and psychedelics. Journal of Psychiatric Research. 2026;193:172-178. doi:10.1016/j.jpsychires.2025.11.021.