One in six people who take cannabis for pain relief say their doctor advised them to use it, a survey suggests.
Young men are most likely to use cannabis for pain relief
The UK survey, published in the International Journal of Clinical Practice, asked just under 1,000 people about their use of the drug.
Almost 70% said cannabis significantly relieved their symptoms - 45% said it worked better than prescribed drugs.
But the British Medical Association said it had never heard of a doctor recommending the drug.
The survey was sent out to people who contacted the company GW Pharmaceuticals because they were interested in its research into using cannabinoids as treatments.
People with chronic pain were most likely to use cannabis for medicinal purposes (25%) followed by patients with multiple sclerosis (22%), depression (22%) arthritis (21%) and neuropathy, or nerve disorders (19%).
Most people used the drug at least once a week with a third of those surveyed said they used cannabis six or seven days a week.
Younger people, men and those who had used cannabis recreationally were also more likely to use cannabis for medicinal reasons.
Two thirds said a friend, or family member had suggested they take the drug, but 16% said their doctor had suggested it.
And 45% said cannabis worked better than prescribed medication.
'Harness the benefits'
Dr Mark Ware from McGill University Health Centre in Montreal, Canada, told the BBC News website: "The results show that people with a wide range of conditions thought cannabis had benefits.
Dr Ware, who conducted his research with GW Pharmaceuticals, added: "To our knowledge this is the most extensive survey of medicinal cannabis use among chronically ill patients conducted to date."
A spokeswoman for the charity Drugscope said: "The medicinal benefits of cannabis have been widely discussed for some time, and pharmaceutical research is ongoing into finding a way of harnessing those benefits in an effective way."
She added: "I suspect doctors do sometimes say to patients that there's nothing else they can currently give them to relieve their pain, but that cannabis could work."
A spokeswoman for the British Medical Association said: "We are not aware of this happening".
But she said the BMA wanted certain cannabinoids - chemicals extracted from the drug - to be legalised for wider medicinal use.