Halifax Researcher Studies How Cannabis Affects Brain Function in Young Adults

Study taking place in Halifax, N.S. and London, Ont.

Aly Thomson · CBC News 

Dr. Philip Tibbo, a professor of psychiatry, is conducting the study with researchers at Western University in London, Ont. It involves 180 people in both provinces between 18-35 who use cannabis to varying degrees.

One group taking part in the study is affected by some form of psychosis, such as schizophrenia, while the other group is unaffected by an illness. 

Tibbo said daily cannabis use, or even in some cases occasional use, has been shown to negatively impact early gains made by people diagnosed with psychosis.

He said he's looking at how cannabis can impact brain white matter — nerve fibres that connect various parts of the brain — during its final development phase in young adulthood.

It also happens to be a time when cannabis use can be quite heavy.

"This will actually give us a little bit better insight into how cannabis can affect brain structure and brain function," he said.

In this practice scan on the brain of a researcher at Dalhousie University's psychiatry department,

white matter is shown outlined in blue. (Submitted by Kyle McKee)

Tibbo said he will look at whether abnormalities form in white matter as a result of cannabis use. Abnormalities in these connections mean your brain is not functioning at peak capacity.

"Each area of the brain doesn't work independently — it's all interacting. It's very complex. If you have more dysfunctional connections, the brain is not working the way that it should be," he said.

"If there's a particular threshold that is met, you could have symptoms of that disconnection, and part of that could be the expression of illness such as schizophrenia."

Using cutting-edge techniques to image the brain, Tibbo will also be monitoring if people within the healthy sample group have unusual experiences, or psychotic-like symptoms, after smoking cannabis.

Dr. Philip Tibbo is a professor of psychiatry at

Dalhousie University in Halifax. (Submitted by Philip Tibbo)

"What I usually say clinically is if you're going to be smoking, you're doing it because it's supposed to be a pleasurable experience," he said.

"But if you're smoking pot and you're getting a bit more paranoid, or you're feeling a little bit more sketchy, well then perhaps there's some vulnerability there to have negative outcomes, and is that because of the effects of cannabis on your brain white matter?"

The research got underway last May. Subjects are being tested at the outset, after six months and after one year.

He said he hopes the study will eventually arm adolescents and young adults with more information to make informed decisions about cannabis use.

The study costs around $500,000 and is being funded through the Canadian Institutes of Health Research and Research Nova Scotia.

Smoking Strong Cannabis ‘Can Lead to Brain Damage,’ Study Finds

© Steve Dipaola / Reuters

Smoking extremely strong cannabis can lead to “significant” brain damage, a King’s College London study suggests.

The study, published in the journal Psychological Medicine, found that “skunk” cannabis damages the corpus callosum, a bundle of neural fibers that allows communication between the brain’s left and right hemispheres.

The two sides of the brain have very different functions. For instance the right hemisphere controls the left side of the body and the left hemisphere controls the right side of the body. While the Bible says, "do not let the left hand know what the right hand is doing", it is speaking metaphorically. In reality, coordination between the two sides of the body is highly recommended. And there are many other reasons the two sides of the brain should be communicating.

In Holland, where marijuana is legally sold in cafes, skunk has been reclassified as a hard drug and is therefore illegal.

The illegal drug contains high levels of tetrahydrocannabinol (THC), the chemical responsible for the high users receive.

"It has long been known that people with a psychotic illness such as schizophrenia are far more likely to smoke both cannabis and tobacco,” Marjorie Wallace, the chief executive of the mental health charity SANE, said.

She added that scientists believe there is a direct link between cannabis and the levels of dopamine, which is the (the chemical messenger in the brain which is related to psychotic experience).

Regular use of the substance can lead to more harm, according to the research.

Frequently smoking the drug could trigger mental health issues, hallucinations and slow down brain activity.

Researchers examined 56 patients who reported having had a psychotic episode and 43 healthy volunteers.

The average age of healthier participants was 27 while the average age of psychotic patients was 29.

Previous studies highlighted much higher incidents of psychosis among teenagers smoking pot than adults. This study, while not determining incidents of psychosis does indicate that it does occur in adults, as well as the damage to white matter.

Lead researcher Dr Paola Dazzan, from the Institute of Psychiatry, Psychology and Neuroscience at King's College London, said: “We found that frequent use of high potency cannabis significantly affects the structure of white matter fibers in the brain, whether you have psychosis or not.

“This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be.”

Co-author Dr Tiago Reis Marques said: “This white matter damage was significantly greater among heavy users of high potency cannabis than in occasional or low potency users, and was also independent of the presence of a psychotic disorder.”

Legalizing pot

Commenting on the findings, freelance journalist Rhiannon Lucy Cosslett said legalizing the drug would give users “far greater control and choice” over the strength of what they smoked.

More than two million people in Britain smoked cannabis last year. A private analysis by the Treasury found that legalizing cannabis would raise tax revenues worth hundreds of millions of pounds and result in huge savings for the criminal justice system.

In August, government ministers debated a petition signed by 200,000 people calling for the legalization of cannabis. Its prohibition was upheld, however.