Could THC in blood and saliva not be as reliable as once believed? 

Measuring THC in blood and saliva has been a popular drug-testing strategy used by Canadian and American enforcement agencies, but researchers working with the University of Sydney have suggested that the relationship might not be as strong as police believe. 

For a long time, police have used THC in blood levels to determine whether not somebody was under the influence of weed. This strategy was chosen because originally, lawmakers believed that weed and blood had the same relationship as alcohol and blood. 

In other words, they based their weed intoxication tests on blood-alcohol tests. 

As weed smokers, we know that the relationship between blood and weed isn’t the same as alcohol and blood. For one, alcohol in blood disappears comparatively faster than THC in blood.

If you’re a chronic weed smoker or edible eater, THC can last up to months in your body through your hair and fat, a relationship that researchers at the University of Sydney agreed with. 

weed in blood and saliva

In a review published in Neuroscience & Biobehavioral Reviews, researchers say that “higher blood THC concentrations were only weakly associated with increased impairment in occasional cannabis users while no significant relationship was detected in regular cannabis users.”

Put more simply, high THC content in the blood does not necessarily suggest intoxication. 

Researchers go on to say that their findings “suggest(s) that blood and oral fluid THC concentrations are relatively poor indicators of cannabis-THC-induced impairment.”

For the study, the researchers collected data from 28 publications involving the consumption of either smoked and/or edible forms of cannabis. They then compared the relationships between THC levels in blood and saliva to driving performance or driving-related skills such as reaction time.

In their tests, they discover that for occasional weed users, there was indeed a relationship between blood and oral fluid THC concentrations and impairment were observed. However, the researchers note that most of these relationships were “weak” in strength. 

No significant relationship between blood THC concentration and driving performance was observed for ‘regular’ (weekly or more often) cannabis users.

“Of course, this does not suggest there is no relationship between THC intoxication and driving impairment,” Dr. McCartney, the lead researcher behind the study said. “It is showing us that using THC concentration in blood and saliva are inconsistent markers for such intoxication.”

McCartney says that their findings raise questions about the validity of the tests used to measure weed impairment, which includes blood testing for THC used to detect impaired drivers in some US states. 

Dr. McCartney said: “Our results indicate that unimpaired individuals could mistakenly be identified as cannabis-intoxicated when THC limits are imposed by the law. Likewise, drivers who are impaired immediately following cannabis use may not register as such.”

The researchers also found that how “stoned” people think they felt was also only weakly associated with actual impairment. 

In other words, your mind might be playing games with you to make you think you’re higher than you actually are!  This also means that drivers should not necessarily rely on how high they think they are when deciding whether they are fit to drive.

Academic Director of the Lambert Initiative, Professor Iain McGregor, said: “THC concentrations in the body clearly have a very complex relationship with intoxication.” 

“The strong and direct relationship between blood-alcohol concentrations and impaired driving encourages people to think that such relationships apply to all drugs, but this is certainly not the case with cannabis.”

So, with weed alcohol being so different, why do police and lawmakers insist on treating them the same? While legalization has made it possible for many more to enjoy the recreational and health benefits of weed, this old line of thinking is extremely damaging and harmful for legal users, and Professor McGregor agrees.

“The increase in legal recreational use of cannabis across multiple jurisdictions worldwide is also making the need for reform of cannabis-driving laws more urgent.”

We already know that cannabis legalization doesn’t cause traffic accidents, so treating weed the same as alcohol only increases the chances that some poor innocent person ends up in prison for driving while completely sober.

The researchers say that their findings can affect how drug-driving laws are implemented and executed around the world, but it’s too early to say whether or not lawmakers will listen to the science or stick to reefer madness

Herb Approach News is the media division of the cannabis health company Herb Approach. Through this medium, we are determined in providing insight on everything cannabis related, from news to commentary, from tips to guides on practical consumption, a whole lot more. Have a question? Email us at [email protected].