The impacts of cannabis use on mental health — particularly on young, developing brains and those with a history of psychosis — must be considered as Canada moves forward with pot legalization, experts say.
Young people’s brains are vulnerable to substances such as alcohol and cannabis, said Dr. Jürgen Rehm, director of the Institute for Mental Health Policy Research at the Centre for Addiction and Mental Health (CAMH).
“There are a number of risks to the developing brain and to impact mental disorders, especially psychotic events,” said Rehm. “The human brain is developing into the 20s.”
A minimum age of 18 for access to marijuana was a key recommendation of a federal task force looking at legalization. The task force’s report, released Tuesday, states that Canadians must be made aware of the risks of consumption.
“The challenge with setting an age limit is always the balance between the potential risks to the brain or to the developing adolescent health versus the risk of the black market,” said task force vice-chair Dr. Mark A. Ware.
The science behind cannabis can be contradictory, Ware said, and a lack of data further complicates the situation. He said the minimum age allows adults to make an informed decision on cannabis use.
“What matters is how we teach parents, children, the public, about what the potential risks and harms of cannabis use are, especially when used very young,” said Ware.
Cannabis harms to mental health
A growing body of evidence has linked cannabis use to psychosis.
Cannabis is often regarded as an “innocuous” drug, a 2001 report in the British Journal of Psychiatry notes. However, evidence shows it carries dependency risks and other adverse effects, “particularly among people with pre-existing psychiatric disorders.”
“People with major mental illnesses such as schizophrenia are especially vulnerable in that cannabis generally provokes relapse and aggravates existing symptoms,” the report states.
A study that followed 45,000 young Swedish soldiers for 15 years found that those who smoked marijuana were more than twice as likely to develop schizophrenia.
Another 10-year follow-up on 2,000 teens entering adulthood found that those who smoked marijuana at least five times were twice as likely to develop psychosis, compared to their non-pot smoking counterparts, according to a 2011 study.
Canada is tasked with moving to a pot legalization model that is combined with a “strict public-health model,” said Rehm.
“We do not believe that cannabis is a benign substance, we do not believe that it does not have any harm, but we believe that with legalized cannabis we are able to minimize those harms than in any other environment.”
CAMH’s 2014 report, Cannabis Policy Framework, which was cited within the task force’s report, urges an evidence-based approach to reducing cannabis harm in Canada.
The risks around driving while under the influence of marijuana, or other activities where a consumer or those around them could be injured, is of also of concern, Rehm said.
“Cannabis has a lot of different health effects,” said Rehm. “Probably the most severe health effect is cannabis dependence.”
Around 100,000 Canadians are currently dealing with cannabis dependency — and that’s before legalization.
Canada already has laws in place for medical marijuana use. Cannabis is often touted for its ability to alleviate symptoms associated with a host of illnesses and conditions, from cancer to multiple sclerosis to the treatment of seizures.
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Marijuana is also commonly used to treat PTSD; Canadian veterans’ free daily allowance was recently reduced to three grams per day from 10.
The federal government’s plan to introduce marijuana legislation next year will make Canada only the second country in the world to legalize pot. The federal government is treading carefully.
“The delivery of the Task Force report is an important step in helping the Government fulfill its commitment to legalize, strictly regulate and restrict access to cannabis,” read a joint statement from a number of federal ministers following the report’s release.
In a submission to the task force, the Canadian Medical Association stressed the need for access to substance abuse and mental health services to be expanded along with marijuana legalization.
“A plan to expand training programs in addiction medicine and access to treatment should be in place prior to legalization,” the CMA submission stated.
Rehm said it’s vital that the federal government use pot revenues, projected to be in the billions annually, for substance abuse education and support services.
“We have to make sure, hopefully there’s a law, that there is a dedicated tax for clinical, education, administration, research and enforcement,” said Rehm. “That has to be done.”