The variability in product choice suggests a lack of consistent clinical guidance, authors say.
Data was collected from the experiences of more than 200,000 cannabis consumers in the US.
"Medical cannabis users had a 74% higher risk of heart rhythm disorders, however, the absolute risk difference was modest."
The condition accounts for between one and two per cent of all childhood-onset epilepsies.
Patients must have access to reliable guidance about medical cannabis from their doctor, say the authors.
Medical cannabis is not associated with an increased risk of psychiatric hospitalisations.
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Synthetic cannabinoids appear to have less appeal in states which have legalised natural cannabis.
"In terms of mental health problems, cannabis appears to be at least as safe as the legal drugs alcohol and tobacco."
Researchers believe cannabis may help mitigate symptoms such as nasal congestion.