Although marijuana may have a reputation as a relatively harmless drug, a new case report links it to the deaths of two young men in Germany.

Toxicological examinations concluded that the men were under the influence of cannabis before they died, and traces of THC — the main active ingredient in marijuana — were found in the men's blood and brain tissue, the researchers wrote in the report.

In both cases, the deaths were related to cardiovascular complications. In one of the deaths, a 23-year-old man without a history of health problems suddenly collapsed while using public transportation, and died after 40 minutes of unsuccessful resuscitation efforts, according to the case report based on postmortem investigations. The man had a small amount of marijuana in his pockets when he was found, according to the researchers at the Institute of Legal Medicine, University Hospital Duesseldorf in Germany, who reported the case.

In the second case described in the report, a 28-year-old man was found dead at home by his girlfriend. An ashtray, rolling paper and a sealable plastic bag containing remnants of marijuana were found next to the body. The man had occasionally used cannabis, the researchers wrote. He had also abused alcohol and drugs, such as amphetamines and cocaine until about two years before his death, they wrote. [5 Bad Habits You Should Still Quit]

"After exclusion of other causes of death, we assume that the young men died from cardiovascular complications evoked by smoking cannabis," the researchers wrote.

"We assume the deaths of these two young men occurred due to arrhythmias evoked by smoking cannabis," but this assumption does not rule out that the men were predisposed to cardiovascular risks, they wrote.

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Nikolas P. Lemos, the chief forensic toxicologist for the San Francisco Medical Examiner's Office, said there have been confirmed cases in which marijuana has had harmful effects on the heart.

"The potential cardiotoxicity of cannabis has been reported in peer-reviewed abstracts as well as scientific proceedings before, including by my team," Lemos said.

"This case report adds two more cases from Germany, but since late last year, we have known and reported on this drug's potential cardiotoxic effects in some parts of the general population," he said.

The researchers in Germany who reported the deaths declined an interview request from Live Science, citing an overwhelming media response to the paper and "some quite unpleasant reactions from individuals."

Following the online publication of the paper, Jost Leune, the head of the German Association for Drugs and Addiction in Hannover, Germany, criticized the report in an interview with the website TheLocal.de, saying, "Cannabis does not paralyze the breathing or the heart."

"Deaths due to cannabis use are usually accidents that are not caused by the substance, but to the circumstances of use," Leune said.

However, other recent research also has linked marijuana use with cardiovascular complications in young and middle-age adults. In a study published in April in the Journal of the American Heart Association, researchers examined data on health complications following marijuana use, gathered from 2006 to 2010 by the French Addictovigilance Network. They found that among the 2,000 cases of reported complications, 35 cases involved heart problems. Among those were 20 people who had heart attacks, including nine who died.

"There is now compelling evidence on the growing risk of marijuana-associated adverse cardiovascular effects, especially in young people," study author Émilie Jouanjus, a medical faculty member at the Centre Hospitalier Universitaire de Toulouse in France, said in a statement at the time. "It is, therefore, important that doctors, including cardiologists, be aware of this, and consider marijuana use as one of the potential causes in patients with cardiovascular disorders."

"It is important that people realize that any drug can have harmful effects," Iain M. McIntyre, a director and chief toxicologist at the San Diego County Medical Examiner's Office, told Live Science.

Some people who are predisposed to cardiac events may be particularly vulnerable to potential harmful effects of marijuana use, and the new report shows this, McIntyre said.

One limitation of the report, however, was that it did not specify for how long the two men had been using marijuana, he said.

The researchers who wrote the report stressed that the risk of cardiovascular effects of marijuana use in the general population is low, but it is higher in people who have cardiovascular issues.

"Persons who are at high risk for cardiovascular diseases are even recommended to avoid the use of cannabis," they wrote.

Lemos said he hopes the report will raise awareness of the potential health complications of marijuana use. "I am delighted to see this additional work in hope that medical examiners, coroners and physicians will realize that they need to collect specimens, test for cannabis in post-mortem fluids and consider the contributions of cannabis in the death investigations.

"We simply cannot, any longer, adhere to the old mentality that 'marijuana does not kill," Lemos told Live Science. "We are now seeing evidence from my office and elsewhere that it just might."

The case report was published in the April issue of the journal Forensic Science International.

Follow Agata Blaszczak-Boxe on Twitter. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

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