EEG Study Finds Stronger Psychoactive Signals From Full-Spectrum Cannabis Than High-Purity THC
A 2023 collaboration between cannabis company PAX Labs and neurotechnology firm Zentrela reported that a full-spectrum cannabis extract produced stronger and somewhat faster EEG-derived psychoactive effects than a high-purity THC oil with a similar THC concentration. The findings are consistent with, but do not prove, the cannabis “entourage effect”—the hypothesis that cannabinoids and other plant compounds can alter one another’s effects.
The company’s study report involved 28 adults who inhaled two standardized puffs, totaling about 8 milligrams, from a PAX Era Pro vaporizer. Participants received either a Blue Dream live-rosin product containing approximately 85% THC along with other cannabinoids and terpenes, or a Berry Gelato distillate product containing about 82% to 85% THC.
Zentrela recorded brain activity from eight regions using a portable electroencephalogram (EEG) headset. Its machine-learning system then converted changes in the recordings into a standardized “psychoactive effect level,” or PEL, ranging from 0% to 100%. This measure is an EEG-based proxy for drug effects; it is not the same as asking participants to rate how euphoric or intoxicated they felt.
According to the report, the live-rosin product produced a measurable response after about three minutes, compared with roughly four minutes for the high-purity THC product. The live-rosin group reached a reported peak PEL of 40% after 15 minutes, while the high-purity THC group reached approximately 19.1%. After 90 minutes, the reported PEL for the live-rosin group remained about 30.2%.
Those results suggest that products with similar labeled THC concentrations can produce different brain-response patterns. However, the experiment does not isolate the cause of the difference. The products came from different cannabis varieties and differed in their overall chemical composition, including their cannabinoid and terpene profiles. The study therefore cannot establish that a particular terpene, minor cannabinoid, or combination was responsible for the stronger signal.
The study was also conducted and reported by companies with a commercial interest in cannabis products and EEG-based product measurement. Its sample was small, and the report is not a conventional peer-reviewed clinical trial published in a scientific journal. The findings should consequently be treated as preliminary rather than as definitive evidence that full-spectrum cannabis reliably produces a stronger or longer-lasting high.
The broader scientific evidence on the entourage effect remains mixed. A 2023 review of the hypothesis concluded that evidence for a stable and predictable effect is limited. Likewise, a laboratory study published in Frontiers in Pharmacology found no clear evidence that several commonly studied cannabis terpenes directly changed THC or CBD activity at CB1 or CB2 cannabinoid receptors.
There is some evidence pointing in the other direction, but it also has important limitations. A 2018 meta-analysis of observational epilepsy studies reported that CBD-rich cannabis extracts appeared to have a better therapeutic profile than purified CBD, including lower reported doses and fewer adverse effects. The authors emphasized that the comparison was based on observational data and that controlled clinical studies were still needed.
For consumers, the PAX-Zentrela results suggest that THC percentage alone may not predict the intensity or timing of a cannabis experience. They do not, however, establish that full-spectrum products are universally more potent, safer, or more effective for medical purposes. Larger, independently funded, peer-reviewed studies that match products more closely and measure both brain activity and participants’ subjective experiences will be needed to determine how reliably the effects of cannabis compounds interact.
