For decades, researchers and clinicians have aimed to understand the relationship between cannabis use and psychiatry. Many have proposed that cannabis use can contribute to the development of psychosis and psychiatric conditions, including schizophrenia. However, the direct relationship between the use of cannabis products and the risk of developing mental health conditions is still not fully understood.
While uncertainty persists, access to medicinal cannabis products for a wide range of symptoms and conditions is gradually increasing around the world. In Australia, it became legal to prescribe medical cannabis in November 2016 through the Therapeutic Goods Administration (TGA). This allows practitioners to apply to the TGA to prescribe a specific cannabis-based product to a patient with a specific indication.
Despite improved availability, establishing the therapeutic potential of cannabis-based medical products (CBMPs) in psychiatry remains a work in progress. The conclusions of existing research remain cautious with systematic reviews citing poor quality and uncertain outcomes across current evidence. With the aim of furthering our understanding of the recent patterns of medical cannabis prescribing for psychiatry-related conditions, a recent study examined the extent to which CBMPs are being accessed via current schemes in Australia.
What Conditions Were Medical Cannabis Prescribed For?
The researchers obtained anonymous data from the TGA through a Freedom of Information request. The TGA approved 297,409 applications for medicinal cannabis between November 2019 and September 2022. During this period, psychiatric conditions represented 33.9% (n = 100,666) of total approvals and two of the top three indications in the dataset behind pain (n = 164,055; 55.2%) (anxiety, n =67,095; 22.6%; sleep disorders, n = 11,202; 3.8%).
Of psychiatry-related indications for which medical cannabis prescriptions were approved, 38 different DSM-5-TR defined psychiatric conditions were represented. The majority of approvals were for anxiety disorders (66.7% of psychiatry-related prescribing), sleep-wake disorders (18.2%), trauma- and stressor-related disorders (5.8%), and neurodevelopmental disorders (4.4%).
Findings of the Study
Approval of CBMPs for psychiatric indications was primarily for younger patients, with approvals for patients aged under 40 representing 60.4% of total approvals (patients aged 25-39 represented 46.2% of psychiatry-related approvals). In contrast, this age group represented only 25.0% of total non-psychiatric approvals.
The researchers note that CBMP prescribing for psychiatric conditions has grown rapidly since November 2019 – as is the case for all SAS-B prescribing – though growth seems to be slowing as of November 2021. Approvals for the prescribing of CBMPs for neurodevelopmental disorders, depressive disorders, bipolar and related disorders, disruptive and related disorders, and substance and related addictive disorders have shown dramatic increases. In contrast, there was minimal approvals for the psychiatric indications of schizophrenia, bipolar disorder, and obsessive-compulsive disorder.
Prescribing for Anxiety Disorders
Anxiety disorders represented the most common psychiatric indication for which medical cannabis was prescribed. The data shows that the use of THC-containing products is widespread which, the researchers note, may give some grounds for concern considering past findings that high doses of THC can induce anxiety and paranoia.
Prescribing for Trauma- and Stressor-Related Disorders
In recent years, a growing amount of research has focused on the therapeutic potential of CBMPs in the treatment of post-traumatic stress disorder (PTSD). Current evidence indicates that self-medication with cannabis is particularly prevalent among patients with PTSD; however, studies in this area have so far yielded mixed results. Nonetheless, trauma- and stressor-related disorders represented a significant proportion of medical cannabis approvals in Australia during the study period.
Prescribing for Sleep-Wake Disorders
To date, evidence for the efficacy of medical cannabis in the treatment of insomnia and other sleep disorders remains inconclusive. Furthermore, most randomised controlled trials (RCTs) of “insomnia” are often secondary to other conditions, such as chronic pain, and are only conducted over acute timelines making conclusions uncertain. Current SAS-B prescribing for insomnia is predominantly for THC-containing products. However, the authors of this analysis note that the majority of support for THC prescribing in sleep disorders seems to be from the community and patient self-report (Lintzeris et al., 2022) as opposed to a robust clinical evidence base.
Conclusions
The growing use of medical cannabis in the treatment of a wide range of indications can be seen as part of a wider trend, both within psychiatry and other areas of medicine. Nonetheless, the authors of this study accept that caution should be practiced when prescribing unregistered medicines and note that official evidence-based guidance on medical cannabis prescribing around psychiatric conditions is needed in Australia.
The researchers conclude with the recommendation that “the discussion must continue with the input of those in the academic and clinical community who are best placed to offer considered and balanced scientific views, with specific effort placed on facilitating high-quality RCTs, particularly where prescribing is disproportionate to existing clinical evidence of efficacy.”
