New UK Study Shows Medical Cannabis Reduces Opioid Use by 40%
A major UK observational study following 1,200 chronic pain patients over 18 months has found that prescribed medical cannabis reduces opioid medication use by an average of 40%. The study, conducted by researchers at King's College London and published in the British Journal of Pain, found that 67% of participants reduced their opioid dosage within six months of starting cannabis treatment, with 23% discontinuing opioids entirely. Researchers say the findings have significant implications for the UK opioid dependency crisis.
A landmark observational study conducted across eight UK cannabis clinics has found that medical cannabis prescriptions are associated with a 40% average reduction in opioid medication use among chronic pain patients — the largest UK study of its kind to date.
The research, led by the Department of Pain Medicine at King's College London in collaboration with the Medical Cannabis Registry, followed 1,200 patients over 18 months. All participants had been prescribed cannabis-based medicinal products for chronic pain conditions including neuropathic pain, fibromyalgia, chronic back pain, and arthritis.
Key findings published in the British Journal of Pain include:
- 67% of participants reduced their opioid dosage within six months of starting cannabis treatment
- 23% discontinued opioids entirely over the 18-month study period
- Average opioid morphine-equivalent dose reduction: 40.3%
- Pain scores (NRS) reduced by an average of 2.1 points (scale 0–10)
- Sleep quality improved in 71% of participants
- Quality of life (EQ-5D) scores improved significantly across all domains
Professor James Collett, lead researcher and head of the Pain Medicine Department at King's College London, said: "These findings are clinically significant. Opioid dependence is a growing crisis in the UK, and identifying effective, safer analgesic alternatives is a national priority. Medical cannabis appears to offer meaningful opioid-sparing effects in a substantial proportion of chronic pain patients."
The study acknowledged limitations including its observational design (no placebo control), potential for selection bias, and the variation in products and doses across the cohort. A randomised controlled trial is now being planned to confirm the findings.
The results add to a growing body of international evidence supporting the opioid-sparing potential of medical cannabis. Similar studies in Canada, Israel, and Australia have reported comparable reduction rates. For UK patients managing chronic pain, our chronic pain guide and clinic comparison provide a starting point.
