Recreational drugs can more than double stroke risk, with a major review suggesting some of the most concerning impacts are among younger people.
Scientists analysed medical data from more than 100 million people and found stroke risk was 122 per cent higher for amphetamine users and 96 per cent higher for cocaine users than for non-users.
Cannabis users were also at greater risk, suffering 37 per cent more strokes than non-users, though researchers found no evidence that opioids, a highly addictive painkiller, added to a person’s risk of stroke.
Dr Megan Ritson, research associate at the University of Cambridge and first author on the study, said: “Illicit drug use is a preventable stroke risk, but I don’t know if young people are aware how high the risk is.
“This is the first finding that has shown how different substance use disorders really can impact stroke risk.”
The rise in strokes linked to some drugs was not limited to older people.
When researchers focused on under-55s, they found a near tripling in stroke risk among amphetamine users.
The additional risk linked to cannabis was a more modest 14 per cent in that age group, while the risk from cocaine was much the same at 97 per cent.
A stroke happens when a blood vessel in the brain becomes blocked or bursts, disrupting blood supply to brain cells and causing them to die.
Stroke is the third leading cause of death and disability worldwide, leading to more than 7m deaths each year, with millions more left with permanent disabilities ranging from paralysis to speech and cognitive impairment.
The researchers pooled data from 32 studies on stroke and recreational drugs, involving more than 100 million people, to see which substances, if any, were associated with greater risk.
This revealed links between drug use and strokes, but it could not prove the drugs were to blame, as drug users may simply be more prone to strokes for other reasons, such as poorer general health.
To delve deeper, the researchers ran more analyses to assess whether drugs were the probable cause of higher stroke risk.
They looked at whether people who were genetically predisposed to having a drug disorder were more likely to suffer a stroke and found they were.
The finding strengthened the suspicion that drugs were to blame, rather than drug users being at greater risk for other reasons.
The drugs appear to raise stroke risk in multiple ways.
Amphetamines and cocaine can send blood pressure soaring, but also constrict blood vessels in the brain, potentially explaining why users are at greater risk of both bleeds and blockages in the brain.
Cocaine also seems to accelerate atherosclerosis, where cholesterol, fat and other substances build up in arteries, causing them to harden and narrow.
Cannabis constricts blood vessels too, and may exacerbate the problem by encouraging the formation of blood clots.
The findings are a concern as global recreational drug use has risen over the past decade.
According to the UN, about 300 million people now consume illicit drugs regularly, with an estimated 228 million using cannabis, 30 million using amphetamines and 23 million using cocaine.
Juliet Bouverie, chief executive at the Stroke Association, said: “These substances put a person’s cardiovascular system under huge amounts of stress which can lead to increased blood clotting, narrowing of blood vessels and damage to the circulatory system, all of which can lead to stroke.
“Regular use of cocaine can also lead to high blood pressure, which is the cause of around half of all strokes.
“More people of all ages are having strokes which is leaving 240 people every day with life-changing disabilities, yet nine out of 10 strokes are preventable.
“We strongly advise that people follow simple steps to live a healthy lifestyle and reduce their risk of stroke including eating a colourful diet, not drinking too much alcohol, getting regular exercise, and not smoking, vaping, or taking any illegal drugs.”
