Medical marijuana was associated with significant improvements in chronic pain, anxiety and post-traumatic stress disorder (PTSD), along with better sleep, mood and quality of life, according to a new study published in Drug Science, Policy and Law. For patients with chronic pain and anxiety who remained in the study, improvements were sustained for up to a year.
Researchers from Torrens University, Western Sydney University’s NICM Health Research Institute, Drug Science, the University of Newcastle, the Medical Cannabis Clinicians Society and Imperial College London conducted the research as part of Project Twenty21 Australia.
The prospective observational study enrolled 522 patients prescribed medical marijuana, including 221 whose primary condition was chronic pain, 222 with anxiety and 53 with PTSD. Participants completed validated questionnaires before treatment and every three months for up to 12 months.
After three months, patients with chronic pain experienced significant reductions in both pain severity and the degree to which pain interfered with daily activities. Average pain severity scores fell from 5.1 to 3.8, while pain interference declined from 5.9 to 4.1. Researchers described the changes as clinically meaningful.
The improvements were particularly large among those being treated for anxiety and PTSD. Average Generalized Anxiety Disorder-7 scores declined from 13.2 to 6.4 after three months, while PTSD severity scores fell from 59.7 to 43.6. The effect sizes were 1.34 for anxiety and 1.44 for PTSD.
Across all three groups, patients also experienced statistically significant improvements in quality of life, perceived overall health, mood/depression and sleep.
Longer-term data were available for 39 chronic pain patients and 31 anxiety patients who completed all 12 months of follow-up. Among those with chronic pain, average pain severity declined from 5.1 at baseline to 3.2 after a year, while pain interference fell from 5.8 to 3.7. Among anxiety patients, average anxiety scores dropped from 13.0 to 5.1. Researchers found the largest improvements generally occurred during the first three months and were maintained through 12 months.
Patients used a range of marijuana products, and using more than one simultaneously was common. THC-dominant flower was the most frequently used category, reported by 48% to 60% of patients at different follow-up periods, while CBD-dominant oils were used by 24% to 38%.
Five adverse events were reported during the study and were classified as mild or moderate, with most associated with high-THC products.
Researchers cautioned that the study had no control group, meaning a placebo effect could not be ruled out. Diagnoses were largely self-reported, outcomes relied on questionnaires, many participants used multiple marijuana products and other medications, and there was substantial attrition over the 12-month follow-up.
Researchers concluded that medical marijuana “may be a useful treatment option” for chronic pain, anxiety and PTSD when other treatments have not been successful, while noting that randomized controlled trials are needed to determine efficacy more definitively.
