For an 11-month-old boy in Denver, ingesting marijuana may have triggered a heart problem that ultimately led to his death, according to a recent report of the case.
If the report's hypothesis is true, the case would mark the first time a person has died from a marijuana overdose. But the findings are far from definitive — as a single case, the report cannot prove that marijuana exposure was actually the cause of the infant's death.
"It's very difficult to say that one [thing] caused the other" in this case, said Dr. Jefry Biehler, chairman of pediatrics at Nicklaus Children's Hospital in Miami, who was not involved in the case.
The boy, who was previously healthy, arrived at the emergency room with slowed breathing, and then went into cardiac arrest, according to the report. Shortly before coming to the ER, the boy had appeared sluggish and irritable, and tried to vomit, the report said.
After the child's cardiac arrest, doctors attempted to resuscitate him for an hour, but he ultimately died.
An autopsy revealed that the boy had myocarditis, or inflammation of the heart muscle. Tests also showed the presence of tetrahydrocannabinol, or THC — the active ingredient in marijuana — in the boy's blood and urine samples. [7 Ways Marijuana May Affect the Brain]
Myocarditis can result from a viral or bacterial infection, but the researchers found no solid evidence of an infection in the child. However, the condition can also result from exposure to drugs.
After extensive tests, THC was "the only uncovered risk factor" for the boy's myocarditis, the report said. This suggests "a potential link between the cannabis exposure and myocarditis" in the boy's case, the authors said. The report was published in March in the journal Clinical Practice and Cases in Emergency Medicine.
In children, marijuana has been found to cause symptoms similar to those seen in the boy, including drowsiness, lethargy and nausea. In addition, it's known that marijuana can have some effects on the heart, such as increasing the heart rate.
There have also been other reports of heart complications tied to marijuana use. For example, last year researchers reported a link between marijuana use and an increased risk of a weakened heart muscle. And in 2014, researchers in Germany linked marijuana use to the deaths of two young men, who both died from heart complications. But the new report is the first to link marijuana exposure to death in a child.
Still, it's possible that other factors could have played a role in the boy's myocarditis, Biehler said. Sometimes, when children are found to have myocarditis, "you never figure out why they had it," Biehler said.
In this case, the boy did have one positive test result for bacteria in his blood, meaning it's possible that bacteria contributed to the myocarditis. But because subsequent tests were negative, the researchers said it's more likely that this result was a false positive, due to contamination of the sample with bacteria from somewhere else.
The researchers also don't know exactly when the child ingested marijuana or how much he ingested, although they estimate that the exposure occurred somewhere between two to six days before his death.
All of these factors "make forming definitive conclusions regarding cause and effect difficult in this case report," Biehler said.
Still, "this report certainly deserves consideration and careful review," Biehler told Live Science. "It is obviously concerning that a child may have developed a lethal side effect after exposure to a substance which has become more widely available after legalization," he said. "It remains vitally important that healthcare providers, public health experts, and families remain mindful of the risks that exposure to substances — legal and illegal — represent to children."
The authors of the new report say their findings justify further research into heart problems linked with marijuana exposure. In addition, in states where marijuana is legal "it is important that physicians not only counsel parents on preventing exposure to cannabis, but to also consider cannabis toxicity in unexplained pediatric myocarditis," they concluded.