Medical Cannabis in Psychiatry: From Neurodiversity to Mental Health

Ahead of Cannabis Health Symposium next month, we examine the research and real-world evidence behind the use of cannabis-based medicines in psychiatry.

Many patients in the UK are now taking medical cannabis for a number of different psychiatric conditions. Data collected through Drug Science’s T21 patient registry over the last few years shows that after chronic pain, anxiety is actually the second most common indication for which cannabis-based medicines are prescribed.

Other mental health conditions such as post traumatic stress disorder (PTSD), depression, substance use disorder and insomnia follow closely behind, alongside neurodiverse conditions such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD).

However, the use of medical cannabis in psychiatry, and the potential risks in this patient population, remains one of the most debated areas of current research and practice. And it’s important to note that this treatment won’t be suitable for everyone, such as those with a previous history of serious psychiatric conditions such as psychosis or schizophrenia 

In what is thought to be the largest dataset of its kind, Canadian researchers surveyed over 7,000 patients authorised to access medical cannabis products. According to their findings, published in 2022 in the journal Psychiatry Research, patients with symptoms of anxiety and/or depression reported sustained improvements following the use of cannabis.

The same year, a pilot study in Australia, found that young people with treatment-resistant anxiety had an average 42.6% reduction in severity and impairment following 12 weeks of treatment with CBD.

Researchers at Washington State University also analysed data from hundreds of people who recorded their symptoms before and after cannabis consumption using the tracking app Strainprint. Their findings showed that in people who self-reported as having PTSD, cannabis reduced the severity of intrusive thoughts by about 62%; flashbacks by 51%, irritability by 67% and anxiety by 57%. A follow-up study reported that users with OCD reported that cannabis reduced their compulsions by 60%, intrusions, or unwanted thoughts, by 49% and anxiety by 52%.

In the UK too, real-world data has previously revealed that the vast majority of patients report improvement in their anxiety or depression symptoms after three months of medical cannabis treatment. 

When it comes to clinical trials, studies are generally small and limited in number, but a few have indicated promising potential. 

Results from a Phase II clinical trial, published in 2022, found CBD to be effective for symptom reduction in patients with anxiety, with few side-effects. Meanwhile, in one of the first human clinical trials on the cannabinoid, CBG [cannabigerol], it demonstrated efficacy in reducing anxiety and stress when compared to a placebo.

Small trials of THC-based medicines in Tourette syndrome have reported reductions in tic frequency and severity, while early work in post-traumatic stress disorder (PTSD) suggests cannabinoids may ease trauma-related nightmares. 

Clinical research in OCD, ADHD and autism remain preliminary. Several trials in children and adolescents have tested CBD-rich formulations, with some studies reporting improvements in clinician-rated disruptive behaviour, social interaction and sleep.

Interestingly, among the most encouraging findings so far come from research on schizophrenia, where several randomised controlled trials of CBD have shown modest but meaningful benefits when used alongside existing antipsychotic medications. 

Speaking to Cannabis Health previously, Dr Niraj Singh, a Consultant Psychiatrist, specialising in Neurodevelopmental Psychiatry, commented: “For many people, medicinal cannabis can offer a great opportunity to improve executive functioning, attention, concentration, as well as emotional regulation alongside reducing anxiety and sleep problems, which are very common in people with neurodevelopmental conditions, as well as in those with other psychiatric conditions. Medicinal cannabis can be effective where there are very few existing treatment options.”

Dr Singh will be delivering a session Exploring the Evidence Base: CBPMs in Psychiatry & Neurodiversity, highlighting key findings, areas of emerging research, and real-world case examples, at Cannabis Health Symposium on Tuesday 25 November. Find out more