One Illicit Drug May Nearly Triple Stroke Risk in Under-55s : ScienceAlert

The most comprehensive analysis yet on recreational drug use and stroke risk has identified three substances of concern – one of which may nearly triple the risk of a blood vessel bursting in the brain.

Researchers at the University of Cambridge in the UK found that participants in a series of studies who recreationally used amphetamines, cocaine, or cannabis were more likely to suffer a stroke than non-users.

Those who used amphetamines faced the greatest risks, but cocaine wasn’t far behind. Cannabis use, meanwhile, showed a lower yet significant stroke risk more in line with heavy alcohol use.

The sweeping systematic review covers the health data of more than 100 million individuals who participated in previous research on recreational drug use. What’s more, additional investigations based on previous genetic studies explored whether the stroke risks associated with drug use might reflect causal effects.

According to lead author Megan Ritson, who studies stroke genetics at Cambridge, the findings provide “compelling evidence that drugs like cocaine, amphetamines, and cannabis are causal risk factors for stroke.”

Amphetamines, in particular, stood out. These drugs are potent and addictive nervous system stimulants that sometimes go by street names like ‘meth’ or ‘ice’.

Bringing together data from eight past studies, Ritson and colleagues found that amphetamine use more than doubles the risk of stroke in adults across all adult age ranges. For people under the age of 55, the risk is nearly tripled.

Combining all ages, recreational amphetamine use increases the risk for ischemic stroke (a blood clot in the brain’s vascular system) by 137 percent. It also increases the risk of hemorrhagic stroke (when a blood vessel bursts in the brain) by 183 percent.

This does not mean that someone who uses amphetamines is doomed to have a stroke, but it does mean their risk may be nearly three times higher than that of non-users.

The relative risk of cocaine use wasn’t far behind. This drug showed one of the strongest negative health associations, nearly doubling the risk of a stroke of any kind and more than doubling the risk for a hemorrhagic stroke in particular.

In an accompanying genetic analysis, further evidence emerged that cocaine use disorder is causally related to cardioembolic strokes and intracerebral hemorrhages, although how the drug may have that effect is not yet clear.

Like amphetamines, cocaine is an addictive central nervous system stimulant that can produce spikes in blood pressure, all while constricting vessels. This may increase the threat that clots pose over time.

“Our analysis suggests that it is these drugs themselves that increase the risk of stroke, not just other lifestyle factors among users,” says genetic epidemiologist Eric Harshfield.

Compared to cocaine and amphetamines, the relative stroke risk for cannabis was found to be much lower but still significant.

While previous studies on cannabis and vascular diseases, like stroke, are conflicting, the current analysis suggests that cannabis use mainly drives an increased risk for ischemic stroke over other types.

Assessing 19 past studies, the researchers have now revealed that recreational cannabis use is associated with a 16 percent increase in a stroke of any kind and a 39 percent increase in ischemic stroke in particular.

In those under the age of 55, stroke risk increases 14 percent with cannabis use.

Interestingly, the analysis found no evidence that recreational use of opioids was linked to an increased stroke risk.

“Illicit drug use is a preventable stroke risk,” Ritson recently told The Guardian science editor Ian Sample, “but I don’t know if young people are aware how high the risk is.”

So far, studies indicate that the chances of a stroke occurring are exacerbated by heavy alcohol use, as well as recreational drug use, such as amphetamines, cocaine, or heroin.

That said, the relative risk varies quite a lot from individual to individual, based on their years of use, amount of use, age, sex, diet, genetics, environment, and socioeconomic status.

Related: Future Risk of Stroke Could Be on Display Inside Your Eyes

“These findings give us stronger evidence to guide future research and public health strategies,” says Ritson.

Even still, the research team does caution that many of the underlying studies in their analysis relied on self-reported drug use, meaning other lifestyle factors could be confusing the results.

Further studies are needed to tease apart all these conflicting factors to see what is really driving the increased risk of stroke, and what warnings and advice might be given to recreational users to best protect their health.

The study was published in the International Journal of Stroke.