A survey has suggested that 1.4 million Brits are using cannabis sourced on the illicit market to treat various health conditions.

The Centre for Medical Cannabis commissioned pollsters at YouGov to survey 10,602 adults on their medical conditions and marijuana use, making it the largest of its kind. It found that 2.8% of adults are using cannabis secured from illegal dealers to self-medicate, which would work out to 1.4 million Brits on an up-weighted basis.

The CMC called for the government to review its stance on medical cannabis in the wake of the results. Founder Steve Moore said the findings quantify what the group has long suspected and urged lawmakers to respond by relaxing the regulations around cannabis prescriptions.

“Other countries such as Denmark and France faced with these same challenges have established national medicinal cannabis pilots – we urge the UK government to do likewise,” said Moore.

The UK legalized medical cannabis in October 2018, but it has only just approved the first two products for doctors to prescribe. Epidyolex became available for British epilepsy sufferers from Jan. 6 after the government fast-tracked it into the National Health Service, while Sativex – a spray containing CBD and THC – has also been approved to treat multiple sclerosis patients.

The CMC survey suggested that 11.82% of Brits suffering from epilepsy use cannabis to self-medicate, along with 19.23% of multiple sclerosis patients. The highest prevalence of self-medication came from people suffering from Huntington’s disease (41.67%), schizophrenia (41.18), and Parkinson’s disease (30.43%).

However, the sample may be too small to draw definitive conclusions on each individual disease. Just seven respondents said they have Parkinson’s disease, along with five respondents suffering from Huntington’s disease. The most common conditions were depression (134), anxiety (120), and chronic pain (69).

Of the 4,916 participants that had stated that they had a medical condition, 281 responded that they currently used cannabis to help manage or treat symptoms of their conditions or side effects brought on by treatment. Of the 281 respondents that said they use cannabis for medicinal purposes, 157 reported using it on a daily basis, 66 on a weekly basis, 24 on a monthly basis, 22 less than monthly, nine answered “don’t know” and three chose “prefer not to say”.

Last year a survey from Maru Voice UK suggested that more than 5 million Brits had consumed cannabis in the past three months, although that included recreational use as well as medical.