Researchers in the United States found that, over a five-year period, regular users in their early 30s were 4.6 times more likely to have a cardiac-related illness than those who did not smoke the drug.
Users in their late 20s were three times more likely to have a heart attack.
Until now, most concerns over the long-term effects of cannabis have centred on its association with mental health disorders, such as depression and schizophrenia.
But this new study, set to be presented at the annual conference of the American College of Cardiology in Washington DC today, fuels concerns that it causes serious physical damage too.
The researchers from Case Western Reserve University in Cleveland, Ohio, unearthed the link after comparing the health records of 210,000 cannabis smokers with ten million non-users.
They noted that users tended to have higher blood pressure than non-users and were more likely to drink heavily, smoke tobacco and have type 2 diabetes – all of which raise the chance of a heart attack.
The so-called case controlled study accounted for these differences by matching people with similar lifestyles.
Lead author Dr Tarek Chami said: "Legalisation of cannabis is growing in support in the US and across the globe, meaning that more cardiologists are going to see patients presenting with the side effects."
"Until now there has been little research into the effect of cannabis on the cardiovascular system, and this is a first step ahead of further studies into the drug."