New discovery could predict medical cannabis impairment

Researchers have discovered a metabolic ‘fingerprint’ which can predict impairment from medical cannabis – pointing to better tests and potentially reducing cognitive effects.

Canadian researchers believe they have found a more effective way to measure cognitive impairment which can occur as a side effect of medical cannabis consumption.

A team at the University of Alberta, has uncovered signature metabolites — much like fingerprints in the blood — which are linked to the cognitive dysfunction and impaired motor skills associated with medical cannabis treatment.

The work could lead to better roadside blood tests for impairment, and could also point the way toward supplements or strains of medical cannabis that reduce impairment while preserving pain management benefits, according to the university’s news website.

A need for better measures

As access to medical cannabis increases and the number of patients grows across the globe, there is a desperate need for more effective and accurate ways of measuring impairment, particularly when it comes to driving laws and workplace drug testing.

Currently drug driving tests in the UK are carried out using swabs, where if THC is detected a blood test is enough to secure a conviction, regardless of whether the driver is impaired or not.

This means that anyone who has consumed cannabis within the last few days – or has been subject to passive smoking – may be over the zero-THC limit and at risk of prosecution.

However, emerging evidence suggests that looking at THC in blood and saliva samples is a poor measure of impairment.

Researchers at the University of Sydney’s Lambert Initiative recently analysed all available studies on the relationship between driving performance and concentrations in blood and saliva of THC. The results indicate that blood and oral fluid THC concentrations are relatively poor or inconsistent indicators of cannabis-induced impairment.

Another study from the University of California San Diego School of Medicine, also found no relationship between blood THC concentrations and driving performance. 

The team at the University of Alberta made the discovery by giving male rats oil containing medical-grade cannabis with and without the active ingredient tetrahydrocannabinol (THC), or just oil with no cannabis.

They then observed their behaviour and examining blood samples to look for a correlation in the metabolites — substances produced when the body breaks down food, drugs or tissues such as fat or muscle.

The researchers noted that animals treated with medical cannabis containing THC had lower levels of butyric acid, a microbial byproduct of digestion, in their blood. 

Principal investigator Jason Dyck, professor in the Faculty of Medicine & Dentistry, director of the Cardiovascular Research Centre, and Canada Research Chair in Molecular Medicine, commented: “We wanted to see if there is a metabolic fingerprint in the serum that identifies if a person is cognitively impaired when they take cannabis.

“We found metabolites that were changed in the same direction that we see in studies of cognitive impairment from other conditions. There seems to be a fingerprint that is more predictive of cognitive impairment than just looking at THC levels alone.”

Reducing unwanted side-effects

The team at the University of Alberta hope the initial findings could not only influence how impairment is measured, but may actually lead to new ways of reducing the cognitive side effects of cannabis, which some patients dislike. 

Pain relief is the main reason patients are prescribed medical cannabis, but many report dissatisfaction with the accompanying cognitive dysfunction, according to research by Dyck and Dean Eurich, professor in the School of Public Health, based on a database of 10,000 medical cannabis users in Ontario.

Dyck added: “Sure, you’re managing your pain, but cognitive impairment means you can’t drive a car, you can’t work and your daily life may be severely affected.”

Dyck and Eurich have done a number of other studies on outcomes for authorised medical cannabis users based on the database, including finding that while the incidence of cannabis poisoning or cannabis-related mental disorders was low, the patients did face an increased risk of hospital visits for cardiovascular events.

The next step for the research team will be to examine whether butyric acid or sodium butyrate supplements could be effective at lessening impairment when taken with medical cannabis.

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