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CBG Can Be a Biomarker to Detect Recent Cannabis Use, Study Suggests

By Alexander Beadle

Published: Apr 03, 2023   
Hand holding a smoking cigarette.

Image credit: iStock

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Assessing the levels of cannabigerol (CBG), a minor cannabinoid, in the blood could be an effective way to detect recent cannabis smoking, a new study suggests.

Published in the journal Clinical Toxicology, the study found that whole blood CBG levels were a “highly specific albeit insensitive biomarker” for recent cannabis smoking.

Levels of CBG remain elevated in the blood for a much shorter time than the levels of other cannabinoids, such as tetrahydrocannabinol (THC), which can remain high well after the intoxicating effects of cannabis have worn off.

This longevity of THC presents a significant issue for those who would like to test for active cannabis intoxication in the case of vehicle crashes or workplace accidents, for example.

As the researchers behind this latest study suggest, testing the blood for CBG could hold promise as an alternative strategy for testing.

Blood levels of CBG rise soon after use

The study, led by researchers from Denver Health and the University of Colorado, took place within a larger investigation of how cannabis smoking affects performance in a driving simulator and in digital psychomotor tests.

A total of 56 individuals were involved in the study, of which 32 reported using cannabis daily and 24 reported using the drug only occasionally within the past month. Each participant was instructed to purchase cannabis flower from their local state-licensed dispensary as normal, bring it to the study site in its original packaging, and then smoke the cannabis how they normally would over the course of 15 minutes.

Immediately before and 30 minutes after use, blood samples were taken from the study participants, which were immediately placed on cold packs and sent to the Colorado State University Analytical Toxicology Laboratory for analysis.

In the baseline blood samples, the researchers did not find any detectable levels of CBG in the occasional users and detected low amounts in only 2 of the 32 daily users. Following smoking, CBG was detected in 28 of the 56 total study participants – 7 out of 24 (29%) of the occasional users and 21 of 32 (66%) of the daily users. These rises may indicate the utility of blood CBG levels as an indicator of recent cannabis use, the researchers say.

CBG is specific “albeit insensitive” for detecting use

Previous research has also found elevated levels of CBG shortly after cannabis smoking, though no sensitivity or specificity values were reported in those studies.

In this new work, the researchers determined that a whole blood CBG concentration of greater than or equal to 0.2 milligrams per liter (mg/L) had 96% specificity, 50% sensitivity, and 73% accuracy for identifying cannabis smoking done 30 minutes prior.

“Our findings indicate that the presence of detectable CBG in blood is a highly specific but insensitive marker of recent cannabis smoking,” the researchers wrote.

“Because acute subjective, psychomotor and neurocognitive effects of cannabis smoking are typically greatest within 30 or 60 [minutes] of smoking inception in subjects for whom such effects occur, CBG may have utility as an adjunct to measurement of other blood cannabinoids for forensic and other related investigations.”

However, the researchers do also note several limitations with their work. Firstly, no information was recorded regarding the amount of CBG present in the cannabis being used, as this is not required under Colorado state laws on product packaging, and so it is unknown how much of this cannabinoid was actually being consumed by each study participant. Participants also recorded their cannabis use outside of this session via means of self-report, and so a lack of external supervision may have allowed participants to misrepresent their normal usage patterns.

Importantly, the researchers also point out that the collection of blood samples 30 minutes after using cannabis for 15 minutes may not reflect the actual realities of forensic scenarios where such a biomarker could be useful. For example, in law enforcement, there is a possibility that a blood sample might not be obtained until one or more hours after any incident of cannabis use.

The trouble with detecting cannabis use

Detecting whether a person is under the influence of cannabis or not is a tricky thing. Unlike alcohol, where effective breathalyzers are already widely available, similar technology for detecting high levels of THC is still largely in a development phase.

But there is another problem standing in the way of those who want to detect cannabis intoxication: THC, the main psychoactive molecule in cannabis, can stay in the body for weeks after its intoxicating effects have worn off.

For instance, in this study, THC was non-detectable in all the participants with a pattern of occasional use, but it was still measurable in nearly 90% of the participants who reported daily use.

The researchers behind this new study report that they are also currently conducting pharmacokinetic studies of different cannabinoids following cannabis inhalation, and investigating how these drugs behave in the body after use. Such information could help to identify other potentially relevant biomarkers for cannabis use.

While this factor was not addressed in this study, it may also be of interest in future work to investigate how broad-spectrum CBD products – which do not cause intoxication but which may contain a variety of minor cannabinoids – might affect blood cannabinoid levels. As the market for CBD products grows more popular, this could present an additional complication if alternative biomarkers for cannabis use are targeted. 


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