VANCOUVER -- Researchers say most youth treated for cannabis poisoning at a British Columbia hospital combined it with other substances such as alcohol, illicit drugs and medication.

Dr. Shelina Babul says 71 per cent of patients seen at BC Children's Hospital for cannabis poisoning in a three-year period before the drug was legalized had used it with other mood-altering substances.

Babul is the senior author of a study on the findings published Wednesday in Health Promotion and Chronic Disease Prevention in Canada: Research, Policy and Practice.

The research includes data collected from the health records of 911 poisoning patients treated in the emergency department between January 2016 and December 2018.

Of that number, 114 patients had consumed cannabis, 29 per cent of them used only that drug, and their average age was 15.

The study says cannabis poisonings were reported most often on weekdays and in the majority of cases, youth smoked pot and drank alcohol in private residences with their friends.