Concurrent Alcohol and Cannabis Use Influences EEG Processing of Alcohol Cues
Authors: Hetelekides Eleftherios , Dickter Cheryl , Bravo Adrian 
Published: September 2022

Background. Concurrent use of alcohol and cannabis (CAM) has been shown to be common among college students (Bravo et al., 2021), and is associated with more alcohol use and related negative consequences (Cummings et al., 2019). There is evidence that both alcohol and cannabis use may be associated with changes in brain functioning and cognition (Oomen et al., 2018), including differences on tasks related to cognitive inhibition/inhibitory control (i.e., Go/NoGo tasks; Lopez-Caneda et al., 2014). A promising method for assessing potential neurocognitive changes associated with alcohol and cannabis use is by examining substance-associated event-related potentials (ERPs) using electroencephalography (EEG; Zhang et al., 2021). The present study aimed to examine differences in P300 ERPs associated with alcohol cues between binge drinking alcohol only students and binge drinking students who also consumed cannabis in the past 30-days (i.e., CAM use). Method. Fifty binge drinking college students (26 of whom also reported using cannabis over the past 30 days) were recruited from a Psychology department research pool to participate in an alcohol-related Cued Go/NoGo task while their brainwaves were measured. The task was characterized by within-subjects factors block (indicating probability of Go/NoGo task cue-target combinations), Cue (Alcohol vs. Neutral), and Target (Go vs. NoGo). Participants identified as mostly White (78%), female (72%), were freshman (64%), and reported a mean age of 18.86 (SD=0.90). To test study aims, at electrode Cz, we conducted a 2x2x2x2 mixed ANOVA with all within-subjects factors (Block, Cue, Target), and between-subjects factor CAM over the past 30 days (CAM use vs. No CAM use). Results. We observed a significant block*target*CAM interaction with a medium effect size (Richardson, 2011), F(1,47)=4.09, p=.049, η2=.08. Cue was retained as a factor in subsequent analyses in order to effectively evaluate the hypothesis. In Block 2, we found a non-significant cue*CAM interaction, F(1,47)=3.10, p=.085, η2=.06, with a medium effect size. Paired-samples t-tests revealed that individuals who used cannabis did not display a significant difference between alcohol and neutral cues, t(25)=0.243, p=.81, while individuals who did not use cannabis showed significantly greater alcohol vs. neutral cues, t(23)=2.34, p=.025. Conclusions. While preliminary, we observed a significant difference in P300 ERPs for alcohol vs. neutral cues, only in individuals who did not report using cannabis over the past 30-days. In other words, we found that CAM using individuals display similar neural reactivity to alcohol compared to neutral cues, while an alcohol vs. neutral difference was observed for alcohol-only individuals. It may be that by using another substance, alcohol stimuli lose salience, and evaluative processing indexed by the P300 is reduced. These are interesting results to be observed within a non-clinical sample of mostly-freshman college students, and provides rationale for examining neuropsychological differences between individuals who use multiple substances versus one substance in populations with more severe levels of dependence.