Neurophysiological and Behavioural Effects of Combined Cannabis Concentrates and Alcohol Among People Who Regularly Use Alcohol and Cannabis.
Eleftherios M Hetelekides, Patricia L Davies, Mark A Prince, William J Gavin, Hollis C Karoly
Addiction Biology November 2026 DOI: 10.1111/adb.70194 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Naturalistic feasibility study Peer reviewed |
|---|---|
| Sample size | 17 |
| Population | Heavy drinking community members who regularly use cannabis (65% male; mean age 31.7 years, SD 10.27) |
| Interventions | Alcohol Cannabis concentrate product |
| Dose | standardized dose of alcohol and a cannabis concentrate product |
| Duration | 4.5-h period with EEG recordings at baseline, 1 h, and 4 h post co-consumption |
| Measures | N1, P2, N2, P3, error-related negativity (ERN), error positivity (Pe) |
| Topics | Cannabis |
| Keywords | EEG/Erp Cognitive function Ecological study Performance monitoring Substance use |
| Registration | NCT06259916 |
| Key points | One hour after co-consuming alcohol and a cannabis concentrate, participants made more errors and responded faster on a visual-flanker task than when sober or in recovery, and EEG amplitudes for P2, N2, P3, ERN, and Pe were smaller than when sober. Performance and neurophysiology measures remained diminished at recovery compared with baseline. |
Abstract
Increasingly potent concentrated cannabis products containing high levels of Δ9-tetrahydrocannabinol (THC) are being consumed with alcohol. This combination is known to acutely impair cognitive and psychomotor abilities, although few studies have evaluated alcohol and cannabis co-use using neural measures. This naturalistic feasibility study explored the acute effects of co-intoxication on behavioural performance and brain activity, measured via electroencephalography (EEG), during a performance monitoring task administered three times over a 4.5-h period.
Participants: (N = 17, 65% male) were heavy drinking community members (age M = 31.7 years; SD = 10.27) who regularly use cannabis. EEG was recorded while participants completed a speeded visual-flanker task at baseline (sober) before consuming a standardized dose of alcohol and a cannabis concentrate product, followed by EEG recordings 1-h (intoxicated) and 4-h post co-consumption (recovery). Recordings were processed to obtain six event-related potential components: the stimulus-locked N1, P2, N2 and P3 and response-locked error-related negativity (ERN) and error positivity (Pe). Repeated measures ANOVAs revealed that behavioural measures at the intoxicated timepoint showed an increase in errors (p < 0.005; η2 p = 0.35) and significant decrease in response time (RT) (p < 0.001; η2 p = 0.50) compared to sober and recovery periods. Measures of brain activity also demonstrated significant change across time with largest amplitudes when sober, smaller amplitudes when intoxicated, then an increase in amplitude to near sober levels at recovery for stimulus-locked (P2, N2 and P3) and response-locked components (ERN and Pe). Thus, compared to sober and recovery periods, the behaviour at the intoxicated timepoint revealed significantly greater impulsivity (RT) leading to significantly higher error rates, while measures of cognitive processing (i.e., decision-making, error detection, performance monitoring/adaptation) showed significantly diminished levels of brain activity. Performance and neurophysiology measures remained diminished at recovery compared to baseline. Understanding neurocognitive functioning during co-intoxication may provide insights into specific cognitive processes that may impact function in everyday activities such as driving.
Trial Registration: NCT06259916.