B.C.'s Chief Medical Officer says marijuana does have some medical benefits, countering claims from federal Health Minister Rona Ambrose that it has no medicinal value.

Last week, Ambrose spoke to On the Coast's Stephen Quinn about the City of Vancouver's plan to regulate marijuana dispensaries. 

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A board shows different products for sale at a medical marijuana dispensary in Vancouver last February. (Jonathan Hayward/The Canadian Press)

Ambrose said the federal government is against the plan, saying science shows conclusively that marijuana is bad for kids.

"We know from the research that marijuana has great harmful impacts on the developing brain for young people, whether it is springing the onset of psychosis or even mental health issues as serious as schizophrenia and this kind of normalization, by having marijuana being sold in storefronts is a terrible signal to young people," Ambrose said on Friday. 

On Monday, Quinn spoke to Dr. Perry Kendall, B.C.'s chief medical officer, and put Ambrose's reasons against marijuana dispensaries to to a scientific test.

Ambrose asserts there is a  connection between the use of marijuana and psychosis and schizophrenia in young people. Does the scientific evidence support that?  

There has been work done recently that suggests there is an increase in risk in psychosis and schizophrenia in young people who have early onset, and fairly heavy use of cannabis. Whether this is directional, in that the cannabis causes the psychosis or the schizophrenia, or people with the tendency towards psychosis or schizophrenia are self-medicating, but whatever the relationship is, we still would not recommend cannabis products be used in developing brains and young people any more than we would recommend them drinking alcohol. If you are going to smoke marijuana under the age of 15 is where we are particularly concerned.

I asked Minister Ambrose if there is any medicinal value in marijuana. She responded by saying, "No medicinal value that a pharmaceutical would." Is that true?

I would beg to differ with the minister there. Cannabis isn't considered medication because it isn't issued with a drug identification number. On the other hand, there are a number of psycho-active and physiological-active compounds in cannabis and if you look on Health Canada's website, there is advice for physicians around prescribing ... and a lengthy list of studies, some of which certainly suggest that there are medical benefits.

Ambrose says the government's aggressive public campaign about the danger of young people using marijuana is working. She says the rate of young people is actually on the decline, in part due to the campaign. Does that to you mean we should stay the course on messaging?

I think the data on drug education messaging is that scary messages do not work. Messages that aren't consistent with people's experiences don't work and in fact they can be counterproductive because people throw out information that is accurate.

These dispensaries have restricted access to people 19 years and older. Does that mean that younger teens will still go through illegal channels to get marijuana?

I would believe so, yes. The argument for legalizing cannabis in a very strictly controlled regime is that you take it out of the hands of the criminal enterprises who have no problem selling it to anybody of any age. In a regulated system, which a public health approach would recommend, you would reserve it for adults. You would know the quantity and quality. You would be able to to take it out of the hands of kids.

There are 80 marijuana-related businesses in Vancouver. Minister Ambrose is calling on the mayor and police to shut these dispensaries down. She says that allowing them to exist sends the wrong message to kids that can only lead to more use and addiction.  Where do you stand on the city's decision to regulate these dispensaries?

I think it is a sensible decision to enact access, to move it away from schools, to be sure you don't have more than one dispensary within 300 yards of another dispensary and to make sure that they are offering a product without pushing the recreational area and they are only selling it to adults.


To listen to the full interview with Dr. Perry Kendall, listen to the audio labelled Fact Checking Marijuana Science.