Smoking cannabis may boost your risk of having a stroke, research suggests.
Researchers analysed hospitalisations of more than two million cannabis users between 2010 and 2014.
Rates of stroke among non-cannabis users didn't change. However, rates among recreational users jumped by 15 per cent.
However, the research was only conducted on adult cannabis users, leaving the scientists unsure if the same risk of stroke applies to children.
Compounds known as cannabinoids in marijuana may cause blood vessels in the brain to narrow, triggering a stroke, the scientists said.
The study comes after the announcement that medicinal cannabis will be available on prescription in England, Scotland and Wales next month.
The dramatic change to policy followed a review into the medicinal status of the drug after high profile cases of patients were being denied products containing THC - the psychoactive compound that makes users 'high'.
Home Secretary Sajid Javid insisted the change, which was announced on October 11, is not the first step towards the broader legalisation of cannabis. However, pressure has grown for the drug to be made legal to smoke recreationally in the UK.
In the US, recreational marijuana is legal in nine states, including California, Colorado and
Massachusetts.
Cannabis can also be taken for medical reasons in 30 US states, such as
Illinois, Florida and
Pennsylvania.
Oklahoma is the most recent state to allow marijuana to be taken on prescription, bringing in the law just last Wednesday.
And in Canada, residents were able to legally buy cannabis for the first time yesterday when a new law came into place.
Avalon University researchers, led by
Dr Krupa Patel, analysed 2.3 million people between the ages of 18 an 84 who used cannabis recreationally and spent time in hospital from 2010-to-2014.
Of these, 32,231 - 1.4 per cent - had a stroke.
And 19,452 had an acute ischemic stroke (AIS), which occurs when blood supply to an area of the brain is suddenly cut off, leading to a loss of cognitive function.
Over the four years, the rate of all strokes among marijuana users rose from 1.3 per cent to 1.5 per cent.
And AIS increased from 0.7 per cent to 0.9 per cent.
Among non-cannabis users, the rate of stroke remained constant throughout the study period.
The research was presented today at the
World Stroke Congress in Montreal.
They scientists believe their findings 'warrant further prospective studies to evaluate the marijuana-stroke association amidst legalisation of recreational use'.
But the study contradicts previous research that suggests smoking cannabis can actually reduce the risk of stroke by boosting blood flow to the brain.
Marijuana has also been linked to faster recovery post stroke.
Stroke is the second leading cause of death and disability globally, with one person passing away from the condition every six seconds.
Around 140,000 people die from stroke in the US and 32,000 in the UK every year.
This comes after research released last year suggested the over-the-counter supplement
ginkgo biloba
boosts memory, muscle strength and speech in stroke survivors.
The herbal supplement
prevents cell death in the brain by improving its blood flow, according to a study by
Nanjing University, China.