The use of medicinal cannabis in Australia has skyrocketed, with approximately 700,000 people turning to it for health benefits in the past year. Sales have quadrupled since 2022. Yet, most products available lack registration with the Therapeutic Goods Administration, bypassing rigorous testing. Safety and effectiveness remain key concerns, particularly for prevalent mental health issues.

Comprehensive Review Examines Effectiveness

A major review published in Lancet Psychiatry analyzes the largest collection of data on medicinal cannabis for mental health and substance use disorders. These conditions rank among the top reasons for prescriptions, including anxiety, sleep disorders, post-traumatic stress disorder (PTSD), insomnia, depression, and attention deficit hyperactivity disorder (ADHD).

Researchers identified 54 randomized controlled trials spanning 1980 to 2025. These gold-standard studies evaluated treatments for disorders such as psychotic conditions, anxiety, insomnia, anorexia, PTSD, and substance dependencies like cannabis, cocaine, and opioids.

Cannabidiol (CBD) featured most prominently, followed by tetrahydrocannabinol (THC) and THC-CBD combinations. CBD offers non-intoxicating effects with a strong safety profile, while THC can cause short-term issues like paranoia and long-term risks including cannabis use disorder.

Key Findings on Treatment Outcomes

Medicinal cannabis proved no more effective than placebos for psychotic disorders like schizophrenia, anxiety, PTSD, anorexia, or opioid use disorder.

Promising results emerged for cannabis use disorder, where oral CBD-THC oils reduced cravings and usage. Individuals switching from high-THC smoked cannabis to these formulations may lower risks of lung issues and other harms.

Study Limitations and Challenges

Positive signals for tic disorders, Tourette’s syndrome, insomnia, and autism spectrum disorder exist but stem from few, low-quality trials. Intoxicating effects often unblind participants, introducing bias. Conflicts of interest appeared in some studies, warranting caution.

Safety Profile in Focus

Common side effects include nausea, dry mouth, and fatigue—mostly mild to moderate. Serious events like psychotic episodes occurred at rates similar to placebos.

However, trials averaged just five weeks, missing long-term risks. About one-quarter of medicinal cannabis users develop use disorders, akin to recreational users. Many real-world products contain high THC levels, which heighten mental health risks, especially for youth.

Implications and Research Gaps

Prior reviews align with these results, showing scant evidence for mental health benefits. Research emphasizes short-term, low-THC trials, contrasting with prolonged, high-THC real-world patterns.

Extended studies and monitoring are essential, particularly for underserved conditions. As regulators review prescribing practices, these insights should guide policies to prevent harm and promote proven alternatives.

Practical Advice for Users

Personal benefits do not contradict the evidence. Patients should consult doctors regularly and explore validated treatments where possible.