Large Australian registry showed medicinal cannabis was safe and effective for at least two years | Research

The takeaway

A registry of 3,961 cannabis-naive patients prescribed medicinal cannabis showed sustained safety and significant improvements in pain, mental health, insomnia, and overall health status for over two years.

Patients and clinicians considering long-term medicinal cannabis, policymakers evaluating medical cannabis programs, and researchers designing clinical trials.

Significant improvements sustained across all outcomes for 2+ years

What the researchers found

Statistically significant improvements sustained over 2+ years across all outcomes: clinical impression (+39-52%), pain interference and severity (22-26%), depression/anxiety/stress (24-28%), insomnia (35%), and physical/emotional functioning (34-37%). 37.3% experienced adverse events, mostly mild (67%) or moderate (31%), with <2% severe and 0.1% serious.

Why it matters

This is one of the largest and longest prospective registries of medicinal cannabis patients, providing real-world evidence of sustained safety and effectiveness in a complex patient population.

The numbers in context

3,961 patients. Median daily dose: 10 mg THC, 22.5 mg CBD. 37.3% had adverse events (67% mild, 31% moderate, <2% severe, 0.1% serious). Pain severity improved 22.2%, pain interference 26.1%. Depression 24.5%, anxiety 25.5%, stress 27.7%. Insomnia 35%. Stable dose and concomitant medication count over 2 years.

How the study worked

Prospective longitudinal registry of 3,961 cannabis-naive patients prescribed oral medicinal cannabis at specialized clinics. Mean age 56.07, 51% female, with multimorbidity (mean 5.14 diagnoses) and polypharmacy (mean 6.26 medications). Validated outcomes collected regularly over two years.

What this study cannot tell us

Observational registry without placebo control, so improvement could reflect placebo effects, natural disease course, or regression to the mean. Patients self-selected for treatment. Attrition over 2 years may introduce survivor bias.

How to read the evidence

Moderate: large prospective registry with validated outcomes, but no placebo control or randomization.

When this study was published

Published in 2022.

The bigger picture

Real-world registry data from thousands of patients complements the smaller, controlled trials by showing what happens when medicinal cannabis is prescribed to complex, multimorbid patients in routine clinical practice.

Questions still open

How much of the improvement is attributable to cannabis versus placebo or other factors? Would benefits persist beyond 2 years? Does the stable concomitant medication count mean cannabis did not replace other treatments?

Common questions

What conditions were treated?

Chronic pain was the most common indication (71.9%), followed by psychiatric conditions (15.4%), neurological conditions (2.1%), and other diagnoses (10.7%).

Were there serious side effects?

Adverse events occurred in 37.3% of patients, but most were mild (67%) or moderate (31%). Less than 2% were severe, and only 2 patients (0.1%) had serious adverse events.

Did patients reduce other medications?

The mean number of concomitant medications did not significantly change over 2 years, suggesting cannabis was used as an add-on rather than a replacement for existing treatments.

Read the original research

A large Australian longitudinal cohort registry demonstrates sustained safety and efficacy of oral medicinal cannabis for at least two years.

PloS one, 17(11), e0272241

View on PubMed ↗Publisher’s paper ↗

Citation

Vickery, Alistair W; Roth, Sebastian; Ernenwein, Tracie; Kennedy, Jessica; Washer, Patrizia. (2022). A large Australian longitudinal cohort registry demonstrates sustained safety and efficacy of oral medicinal cannabis for at least two years.. PloS one, 17(11), e0272241. https://doi.org/10.1371/journal.pone.0272241