Understanding the Many Effects of Cannabis
Youth & cannabis are a dangerous mix: Early regular exposure interferes with brain development, increases mental health risk.
Brain imaging studies underway at NSHA are shedding light on how cannabis affects the young, still-developing brain.
“The brain does not finish developing until the mid-20s,” notes lead researcher, psychiatrist Dr. Phil Tibbo. “Our research is revealing how cannabis interferes with this process.”
Dr. Tibbo’s research team aims to understand how cannabis—particularly THC, the cannabinoid that produces the psychoactive high—weakens neural connections in the developing brain. These weakened connections make young cannabis users more vulnerable to serious mental health problems like schizophrenia.
“Early exposure to cannabis magnifies the risk of psychosis by four to twelve times,” says Dr. Tibbo, explaining that psychotic episodes (in which a person loses touch with reality) are an early symptom of schizophrenia. “The degree of risk varies depending on family history of mental illness, how young the person started using, how often they use, and how high the percentage of THC in the cannabis they use.”
The white-matter connection
Brain-imaging studies have shown high concentrations of cannabinoid receptors in the white matter of young people’s brains, compared to older adults. White matter—comprised of cable-like bundles of nerve fibres (axons) insulated by a protective sheath of fatty tissue (myelin)—connects the various regions of the brain.
“Cannabinoid receptors in the white matter are designed to work with endocannabinoids, chemicals our brains produce naturally,” Dr. Tibbo says. “Endocannabinoids play a vital role in the normal completion of the brain development process.”
Unfortunately, when the body’s own endocannabinoids are replaced with cannabinoids from an outside source— namely, the cannabis plant—brain chemistry is thrown out of balance and brain development does not complete properly.
“Early, regular cannabis exposure can change the microstructure of the white matter,” Dr. Tibbo explains. “Instead of the axons lining up in uniform bundles of fibres all running in the same direction, we see crosshatching fibres that impede the flow of electrical signals through the white matter.”
New directions in brain imaging
Dr. Tibbo and his team are working with the Biomedical Translational Imaging Centre (BIOTIC) at the QEII Health Sciences Centre and collaborators in London, ON, to launch a $495,000 Canadian Institutes of Health Research-funded study. This will use new brain-imaging protocols to examine the white matter of four groups of young people: patients with early-phase psychosis who regularly use cannabis, those who do not, volunteers with no diagnosed mental illness who regularly use cannabis and those who do not.
“Given the strength of some of today’s strains—as high as 20 to 30 per cent THC, —there is a huge need for continued research support and education."
“We will be one of the first groups in Canada to use this new analysis method in a mental health study,” notes Dr. Tibbo. “It will allow us to uncover and understand the white matter abnormalities associated with cannabis use in early-phase psychosis, separate from the illness effects and cannabis effects alone.”
Advanced brain imaging techniques also position the researchers to assess the effects of medications on the white matter of the brain—for example, new agents to help with myelin repair. “It may be possible to reverse the effects of cannabis on the white matter, if the structural changes are identified and treated early enough,” Dr. Tibbo says. “This could prevent an enormous amount of suffering and dysfunction.”
The politics of cannabis
The legalization of cannabis for recreational use has opened up the conversation and the ability to study the effects of the dozens of compounds found within the plant, says Dr. Tibbo, who presented his work on the ties between early cannabis use and psychosis/schizophrenia to the Canadian Senate.
“Some cannabinoids may be beneficial, but THC is not one of them when it comes to the developing brain,” he says. “It is the primary psychoactive component that disrupts the white matter in young users. Given the strength of some of today’s strains—as high as 20 to 30 per cent THC, compared to 1.5 per cent in the 1970s—there is a huge need for continued research support and education.”
Harnessing the Pain-Relief Power of Cannabionoids
NSHA clinicians and scientific colleagues at Dalhousie have been studying cannabinoids and their receptors for more than 20 years, to harness the pain-relieving power of cannabinoids in safe and effective products.
"Cannabinoids have proven to be profoundly analgesic in acute and chronic pain, both neuropathic and inflammatory,” says Dr. Mary Lynch, director of research at the QEII Pain Management Clinic. She co-founded Panag Pharma with anesthesiologists Dr. Orlando Hung & Dr. Christian Lehmann and pharmacology researcher Dr. Melanie Kelly, in 2014.
So far the company has developed THC-free topical creams for arthritis, as well as drops to combat pain and inflammation in the eye.
“Topical products are safer than oral medications and can target pain without the side effects of non-steroidal antiinflammatories or other systemic medications given,” notes Dr. Lynch.
NSHA anesthesiologist Dr. Karim Mukhida is running a clinical trial of the company’s first product—a topical cream using cannabinoids derived from clover—to see if the cream relieves pain in patients with osteoarthritis of the knee.