THC Was the Primary Active Ingredient in Marijuana While CBC and CBD Concentrations Made No Difference | Research

The takeaway

In a controlled study of 23 healthy users, varying concentrations of cannabichromene (CBC) and cannabidiol (CBD) in smoked marijuana did not change subjective, behavioral, or brain activity effects, confirming THC as the primary active constituent.

Read this if you are interested in whether different cannabinoids in marijuana interact to produce different effects.

Varying CBC and CBD concentrations produced zero changes across all subjective, behavioral, and brain measures

What the researchers found

Twenty-three healthy marijuana users (12 men, 11 women) participated in four sessions where they smoked marijuana cigarettes under blinded conditions. Participants were assigned to low (1.8%) or high (3.6%) THC groups and received cigarettes with varying levels of CBC (0.1% vs 0.5%) and CBD (0.2% vs 1.0%).

Compared to placebo, active THC cigarettes produced expected effects on mood, behavior, and brain activity. EEG and ERP measures showed decreased performance, reduced EEG power, and attenuated attention-related ERP components during working memory and episodic memory tests.

Most effects were not dose-dependent between the two THC levels. Critically, varying the concentrations of CBC and CBD did not change any outcome measures, supporting the conclusion that THC and its metabolites are the primary active constituents of marijuana.

Why it matters

The finding that CBC and CBD concentrations did not modulate the effects of smoked marijuana challenges the "entourage effect" hypothesis at these dose levels. It also validates the use of neurophysiological measures (EEG, ERP) as biomarkers for THC effects in research settings.

The numbers in context

23 participants (12 men, 11 women). Four sessions each. THC groups: 1.8% vs 3.6%. CBC: 0.1% vs 0.5%. CBD: 0.2% vs 1.0%. No dose-dependent THC effects on most measures. No CBC or CBD effects on any measures.

How the study worked

Randomized, blinded study of 23 healthy marijuana users across four sessions. Participants smoked placebo or active cigarettes with varying THC (1.8% vs 3.6%), CBC (0.1% vs 0.5%), and CBD (0.2% vs 1.0%) concentrations. Measures included subjective reports, cognitive task performance, EEG, and event-related potentials during working memory and episodic memory tasks.

What this study cannot tell us

The CBD and CBC concentrations tested were relatively low compared to some cannabis preparations. The study used only two THC dose levels that may not have been different enough to detect dose-dependent effects. The sample size was modest at 23 participants. Only acute effects were measured.

How to read the evidence

Randomized, blinded, placebo-controlled study with EEG/ERP biomarkers. Well-designed but modest sample size and relatively low CBD/CBC concentrations tested.

When this study was published

Published in 2005. Cannabis potency has increased dramatically since then, and interest in CBD and other minor cannabinoids has grown substantially.

The bigger picture

The idea that different cannabinoids interact to produce different effects (the "entourage effect") has been widely discussed. This controlled study found no evidence for CBC or CBD modulating THC effects at the concentrations tested, though the CBD levels used (0.2-1.0%) were relatively low compared to some modern cannabis products.

Questions still open

Would higher CBD concentrations produce detectable modulation of THC effects? Does the entourage effect require specific cannabinoid ratios not tested here?

Common questions

Does CBD change the marijuana high?

At the low concentrations tested in this study (0.2-1.0% CBD), no differences were detected in any subjective, behavioral, or brain activity measure. However, modern CBD products often contain much higher concentrations than those tested here.

What is the main active ingredient in marijuana?

This study confirmed THC (delta-9-tetrahydrocannabinol) and its metabolites as the primary active constituents, as varying the other cannabinoids tested (CBC and CBD) did not change any outcome measures.

Read the original research

Neurophysiological and subjective profile of marijuana with varying concentrations of cannabinoids.

Behavioural pharmacology, 16(5-6), 487-96

View on PubMed ↗

Citation

Ilan, A B; Gevins, A; Coleman, M; ElSohly, M A; de Wit, H. (2005). Neurophysiological and subjective profile of marijuana with varying concentrations of cannabinoids.. Behavioural pharmacology, 16(5-6), 487-96.