The legalization of marijuana for recreational and medicinal use has become more widespread. But findings from a case study about a 70-year-old man who suffered a heart attack after ingesting a lollipop with a hefty dose of THC, published in the Canadian Journal of Cardiology, prompted physicians to stress the need for the public to become more educated about the risks of consuming the drug in various formulations, reports Medical News Today.

Also known as tetrahydrocannabinol, THC is the psychoactive substance in cannabis that gives users a high.

The patient, who was on cardiac meds and lived with stable coronary artery disease, ate almost all of the candy, which contained 90 milligrams of the psychoactive substance. (He consumed the edible marijuana to help reduce pain and improve sleep.) But this huge amount of THC caused him to experience anxiety and hallucinations, boosted his heart rate and blood pressure and caused his body to release a stress hormone—events that were likely responsible for his heart attack.

Previous accounts about similar occurrences, which focused mostly on younger individuals, showed a connection between consuming marijuana and serious cardiovascular events, ranging from an irregular heartbeat to stroke to sudden death.

The current findings, however, led doctors to caution people—especially older ones—to opt for the smallest doses of THC and warn those with heart conditions to avoid THC altogether and instead consider products with CBD, or cannabidiol, marijuana’s nonpsychoactive component, which has been linked to various benefits.)

In addition, physicians stressed that patients should think carefully about their level of tolerance for cannabis and the ways they consume the drug.

“Marijuana can be a useful tool for many patients, especially for pain and nausea relief,” said Alexandra Saunders, MD, of Horizon Health Network’s Department of Cardiology in New Brunswick, Canada, and an author of the article. “At the same time, like all other medications, it does carry risk and side effects.”

Click here to read more about what older folks think about marijuana for medical use.