Project Twenty21 Australia: Results of a prospective observational study of patients prescribed medicinal cannabis for chronic pain, anxiety and post-traumatic stress disorder
Authors
Kylie O’Brien, Justin Beilby, Michael Lynskey, Michael Barnes, Anne Schlag, and David Nutt
Published
August 10, 2026
Abstract
Medicinal cannabis (MC) became legalised in Australia in 2016, yet relatively little is known about its longer-term effectiveness within the Australian context.
Methods
Project 2021 Australia was a prospective observational cohort study that collected data on patients prescribed MC (from as Product Formulary) for four conditions: chronic pain, anxiety, post-traumatic stress disorder (PTSD) and multiple sclerosis (MS) via validated questionnaires (baseline then 3-monthly for up to 12 months).
Results
At study end, a total of 522 patients had enrolled: 221 (42.3%) reported their primary complaint was chronic pain, 222 (42.5%) anxiety, 53 (10.2%) PTSD and 26 (5%) other conditions. Three-month data for chronic pain, anxiety and PTSD indicate MC is effective at reducing primary symptoms as well as improving quality of life (QoL), sleep, mood/depression and perceived overall health (insufficient data for MS). In chronic pain patients, effect sizes (Cohen's d) at 3 months were 0.75 for pain severity and 0.8 for pain interference (BPI questionnaire), for anxiety patients, 1.34(GAD-7 questionnaire) and for PTSD patients 1.44 (PTSD Checklist-Civilian Version), and there were also significant improvements across other measures, including QoL, perceived overall health, mood/depression and sleep, with effect sizes ranging from 0.54 to 1.15. Twelve-month data for chronic pain and anxiety patients indicates that MC use is associated with improvements in primary symptoms, QoL, perceived overall health, mood/depression and sleep quality (insufficient data for PTSD and MS).
Conclusion
MC may be a useful treatment option for conditions, including chronic pain, anxiety and PTSD, where other treatments have not been successful.
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