Early use of marijuana can increase its negative health impacts

But one of the most contentious aspects of legalization is age. A report by the Canadian Task Force on Cannabis Legalization and Regulation, released in December 2016, recommends marijuana use be restricted to those 18 years old and older.

The need for age guidelines falls in line with a new study by James McIntosh, professor of economics in the Faculty of Arts and Science. Recently published in the journal Health, the findings show that young users report the most impact to their physical and mental health.

The article also shows that those who wait until the age of 21 to use the drug are unlikely to develop a lifelong habit.

Heightened risks for youth

For the study, McIntosh and his co-author Rawan Hassunah (BA 16) examined the results of three national surveys on tobacco, alcohol and drug use -- two in Canada and one in the United States.

"We wanted to see what the effects of regular marijuana use were on self-reported physical and mental health," McIntosh explains.

The report cites other studies demonstrating the negative impacts of marijuana. It's the first, however, to look so closely at age of first use.

In terms of overall effects, the study confirmed that marijuana does affect people's physical and mental health, that it will cause cognitive impairment, memory loss, diminished IQ, limited educational success and likelihood for developing mental illness. Physically, early users also suffer higher rates of respiratory diseases and certain cancers.

McIntosh says the younger you start, the worse the impacts.

"We found that if age of first use is below 15, it's always bad for you."

The argument for legalization

So how can these findings translate into informing youth about the risks? Besides legislation, McIntosh recommends educational programs, counselling services and a distribution system that minimizes use by young people.

Despite his warnings about age restrictions, however, he says legalization will bring more good than harm.

"The task force outlines these benefits -- to take marijuana out of criminal hands, to tax it, to make sure that product quality is preserved."

McIntosh adds that being at the cusp of legalization puts Canada in a unique position to begin rigorous study of cannabis and its effects.

"We need to start collecting data on it to see what the effects are on people of all ages. You can get all kinds of information on drinking behaviours -- they should do that with marijuana."