The brain on cannabis

Research rushes to catch up with legalization

The brain on cannabis

Marijuana is set to become legal across Canada this week, and Canadians must be well equipped to confront any downstream effects this historic move may have. 

The Canadian Tobacco, Alcohol and Drugs Survey found 3.6 million — 12 per cent of Canadians — used cannabis in 2015. Of that population, 24 per cent said they used cannabis for medical purposes. 

Following legalization, individuals should be more cognizant of the effects of marijuana, and specifically ways in which it can affect the brain. 

What does marijuana do to your brain? 

The endocannabinoid system is a complex signaling system in the brain and surrounding tissues. Though it is not well understood, it has been shown to play a role in immune functions and the development of the nervous system. It is also the system that processes cannabis and plays a role in producing the associated neurological effects. 

The system consists of endocannabinoids, cannabinoid receptors, and enzymes that transform endocannabinoids in the body. 

Broadly, endocannabinoids like anandamide and 2-arachidonoylglycerol are a class of cannabinoids — chemicals present in cannabis — that bind to receptors in cells. Once bound, endocannabinoids act on CB1, a cannabinoid receptor that is found in the brain. 

Cannabidiol (CBD) and tetrahydrocannabinol (THC) are the two most well described cannabinoids in marijuana. 


CBD does not produce any of the psychoactive effects, and has been found to block some of the effects of THC by interfering with CB1 receptors. 

Structurally, THC is similar to anandamide — a naturally occurring endocannabinoid — and has been shown to activate the endocannabinoid system. 

“[CB1 receptors] are found in many brain regions that control mood, appetite, memory etc. They inhibit the release of an inhibitor transmitter called GABA and this can lead to increased activity of certain brain excitation pathways,” U of T Professor Ruth Ross explained in an email. 

Ross’ research investigates the molecular pharmacology of cannabinoids. 

“There are many unanswered questions about the safety and efficacy of cannabis as a medicine and about the possible harms of cannabis ­— especially for certain people who may be vulnerable to these effects,” Ross added. “We desperately need more solid clinical data from double blind placebo controlled studies on safety and efficacy.” 

Marijuana in other areas of medicine

There is hope that medical research with cannabis and recreational users will benefit from its legalization. 

For example, Ross and her team are working on developing “medicines that target the endocannabinoid system for the treatment of liver disease, pain and brain disorders.”

Ross said that many medical claims are made about cannabis, but it can actually make some conditions worse. 

“It is almost unknown of any person who has overdosed on cannabis,” Andrea Furlan, Associate Professor in the Faculty of Medicine and Staff Physician and Senior Scientist at the Toronto Rehabilitation Institute, wrote to The Varsity. 

According to Ross, “Cannabis even at high doses does not have the type of physiologically dangerous effect that we might see with opioids, which cause respiratory depression and can cause death.” 

However, because of the psychoactive effects associated with marijuana, it could result in “acute psychosis, paranoia, anxiety, or fear,” and such effects could cause harm to individuals or those around them. 

Despite low chances of overdosing on marijuana, several studies have sought to compare long-term use of cannabis versus alcohol in the developing adolescent brain. One study concluded that “lasting effects of adolescent cannabis use can be observed on important cognitive functions and appear to be more pronounced than those observed for alcohol.”

The Canadian Institutes of Health Research is prioritizing research on neurodevelopment, prevention, harm and treatment of problematic cannabis use, potency and product safety, social determinants of health, relationship of cannabis use and mental health, potential applications of cannabis, and pain management. 

“We hope that with legalization there will be more scientists interested in this area, and that Canada will be a leader in research in the world,” Furlan said. 

Weeding out the high drivers

Procedures surrounding roadside cannabis testing is hazy, but new tech developments hold promise

Weeding out the high drivers

When the Cannabis Act comes into effect on October 17, it brings with it a slew of changes to laws regarding possession, distribution, and the selling of cannabis in Canada. 

Some laws, however, will not be changing. Driving under the influence of cannabis is and will remain illegal after October 17, and rightfully so: several statistics show that driving under the influence of cannabis significantly increases the risk of vehicle crashes, especially fatal ones.

Driving high is not uncommon either. A Health Canada survey from 2017 reported that 39 per cent of individuals who use cannabis had driven a vehicle two hours after smoking marijuana. 

This summer, Parliament passed Bill C-45, which clarified the legal amount of tetrahydrocannabinol (THC) — the molecule responsible for getting you high — allowed in the blood while driving. Having two to five nanograms of THC per millilitre of blood constitutes a summary offence. Having more than five nanograms could get you jail time. Still, the procedure for determining drug impairment on the road remains hazy.

Current testing procedures

Law enforcement in Canada currently monitors drug impairment on the road in the same way it does alcohol. If a police officer suspects that you are driving impaired — whether from observing abnormal driving behaviour or simply smelling drugs or alcohol on you during a traffic stop — they can have you take a Standard Field Sobriety Test (SFST). This test, much like an acrobatics audition, will test your balance and coordination. 

You might also undergo a drug recognition evaluation (DRE). Here, if alcohol impairment is suspected, a breathalyzer is used. If not, you can be physically examined for evidence of drug use like having your pupil size measured. Lastly, a toxicological sample, like urine, saliva, or blood, is sent to a forensic lab for examination.

One of the most glaring differences between testing for alcohol impairment versus cannabis impairment is that the former is rapid — alcohol impairment can be determined on the roadside — but impairment by any other drug, including cannabis, is determined after the toxicological sample has been examined. 

The absence of a rapid roadside drug test is concerning, considering the prevalence of drug-related car crashes and the subjectivity of the SFST and DRE. According to Mothers Against Drunk Driving, in 2014, there were twice as many fatal vehicle crashes involving drugs than crashes involving alcohol. Cannabis accounted for 45 per cent of all these drug cases. 

Take your breath away

Several companies are developing cannabis breathalyzer technology, including SannTek, which is based in Kitchener.

SannTek’s breathalyzer is currently being marketed to industries in which drug impairment poses a safety issue, like mining, transportation, and construction, with hopes that law enforcement will follow. Noah Debrincat, CEO and co-founder of SannTek, wrote that the advantage of using breath as a testing medium is that it can only measure recent drug use.

“The advantage… is that it actually correlates to when a user would experience the acute impairing effects of cannabis. Contrast this with the use of something like urine tests, where a person could use recreational cannabis safely on Saturday night, and on Monday would fail a urine test requested by an employer, even though they are not impaired,” wrote Debrincat.

Vivienne Luk, an assistant professor at UTM and forensic toxicologist, says that cannabis breathalyzers have limitations. “There is limited research on the relationship between THC concentration in the breath and its relation with other bodily fluids, like blood,” wrote Luk.

Luk, who regularly testifies in court as an expert witness, says that the functionality of drug screening devices is often questioned in court. “Would smoking, using breath mints, or chewing gum interfere with the functionality of the device? These are questions that are often asked in court cases involving the alcohol screening devices, so I am certain THC ‘breathalyzers’ will also be subjected to similar questioning.”

Saliva sensors have been recently approved by the federal government for roadside cannabis testing, and Toronto police have already completed pilot programs with them. The saliva sensors have similar limitations to breathalyzers: drug concentrations in your saliva can be a diluted representation of what is actually in your blood, potentially leading to underestimations and false negatives.

Other bodily fluids

If breath and saliva are potentially out, what bodily fluid is left? U of T professor Andreas Mandelis from the Department of Mechanical and Industrial Engineering says that interstitial fluid is the answer. 

Mandelis, whose lab is developing a non-invasive cannabis sensor, says interstitial fluid, the fluid surrounding all the cells in your body, carries an accurate ‘memory’ of substances that are in your blood. For THC, it only takes several minutes after it reaches your bloodstream for it to reach the interstitial fluid.

Mandelis and his team measure interstitial fluid THC levels using technology based on infrared radiation. To understand how this works, bear with me for a quick refresher on high school physics.

All materials and objects absorb and emit infrared radiation. This includes our own bodies: humans are constantly emitting infrared radiation, which, unlike light, is invisible to the naked eye. Instead, it is perceived as heat. 

“It’s like in the movie Predator, where the predator couldn’t see in the visible light range but could see in the infrared range,” said Mandelis. “That’s why Arnold Schwarzenegger put mud on his face and body so that he would not be detected… It’s exactly those thermal photons we are looking at.”

What is not explained in Predator is that sometimes the wavelength in which a material — or even a molecule — emits radiation is distinct enough that it can be used to identify that material or molecule. “At that wavelength, at that peak, that only belongs to one molecule,” said Mandelis. This means that if the titular antagonist from Predator had a more sophisticated sensor, it could have identified Schwarzenegger as Schwarzenegger, not just as ‘human.’ 

Thankfully, Mandelis does have a more sophisticated sensor. In order to obtain that specific signature from THC, Mandelis’ sensor directs a laser at your fingertip. Once the laser penetrates to the interstitial fluid — just several microns below the surface of your skin — any THC molecules present will absorb the laser light and re-emit it as infrared radiation at a frequency that is specific to THC. 

“Once the heat is emitted, I have an infrared sensor that can monitor that,” said Mandelis.

Here lies another benefit of testing interstitial fluid to monitor THC concentrations: it is non-invasive. In other words, you can measure the level of THC in your body without actually pricking, poking, or taking any sort of tissue or fluid sample.

Moving forward

Be it a breathalyzer, saliva sensor, or infrared detector, we may have some type of roadside cannabis sensor soon. While technological advancement is important, we cannot forget the human and physiological factors. Luk explains that the levels of THC in your body may be influenced by the user profile. Whether you are an occasional or chronic smoker and whether you smoke or ingest cannabis can influence how much THC ends up in blood, how quickly, and for how long.

For now, Luk suggests that we do not abandon our current roadside methods. “It is important to keep in mind that these devices are designed for screening purposes only, meaning a positive result is a tentative finding and confirmation with a more accurate technique is required.”