The Scientists in France, who tracked more than 1,300 patients in intensive care, found people who took cannabis alone had almost twice the risk of suffering a cardiovascular event. 

Experts today urged hospitals to screen all emergency room patients for recreational drug use.   

Scientists have previously suggested the active ingredient in cannabis, THC, triggers the body's fight-or-flight response, which raises heart rate and blood pressure. 

Over time, this damages the heart and increases the risk of life-threatening problems like heart attacks.  

In the study, researchers tracked 1,392 patients who were admitted to 39 different intensive care units in France over a two-week period in April 2021. 

Among them, 11 percent (157) tested positive for recreational drug use, including 136 with cannabis.   

The other 21 were found to have heroin, cocaine, amphetamines, or MDMA in their system. 

More than a quarter (28.7 per cent) tested positive for two or more of these drugs. 

Over a follow-up of a year, the researchers discovered seven per cent (94) of patients experienced a serious cardiovascular event including death. 

Of the 713 patients in total hospitalised for acute coronary syndrome, 96 (14 per cent) had a positive recreational drug test and 50 (7 per cent) experienced serious cardiovascular events. 

Computer modelling found recreational drug use was 'associated with a three times higher risk of serious cardiovascular events', the scientists said.

They also found that among recreational drugs tested, MDMA had a cardiovascular event risk of 4.1 times that of not taking any drugs. Heroin stood at 3.6 times and cannabis 1.8 times.  

'Other drug types did not have a statistically significant relationship with serious cardiovascular events,' the researchers added. 

Study author and doctor at Hospital Lariboisiere in Paris, Dr Raphael Mirailles said: 'Recreational drug use was associated with a tripling of the risk of a repeat serious cardiovascular event within one year.'

He added: "There is an increasing amount of data regarding the worst prognosis associated with recreational drug use, not only in cardiac intensive care units but also in conventional intensive care units."

"Despite the high rate of underreporting of recreational drug use, systematic screening is not recommended by the current guidelines. It might improve risk stratification of patients and personalised care to favour drug withdrawal. Therefore, systemic screening should be considered in intensive care."

Scientists are still working to unravel exactly why this cardiovascular risk occurs, though it's thought that THC activates the body's fight-or-flight response, which typically occurs during stress or fear.

When fight-or-flight is triggered, it leads to higher heart rate and blood pressure.  

Over time, this causes the heart to need to work harder to pump blood to the rest of the body.

This can wear away at the heart and lead to conditions like heart disease and stroke.  

The scientists will present their research on August 31 at the 2024 European Society of Cardiology Congress in London.