Background: The aim of this study was to assess the relative effects of alcohol mixed with energy drink (AmED) versus alcohol alone on cognitive performance across the ascending and descending breath alcohol concentration (BrAC) limb using doses similar to real-world intake.

Methods: Using a single-blind, placebo-controlled, crossover design, 19 participants completed 4 sessions where they received: (i) placebo, (ii) alcohol, (iii) AmED 500 ml energy drink (ED), and (iii) AmED 750 ml ED. Performance on measures of psychomotor function (Compensatory Tracking Task [CTT]), information processing (Digit Symbol Substitution Task [DSST]; Inspection Time Task [ITT]), and response inhibition (Brief Stop-Signal Task [Brief SST]) was assessed at ~0.05% ascending BrAC, ~0.08% peak BrAC, and ~0.05% descending BrAC.

Results: The ITT and Brief SST showed no differential effect of AmED versus alcohol (gs < 0.30 and gs < 0.36, respectively). Moderate magnitude improvements in alcohol-induced impairment of CTT and DSST performance were observed after AmED versus alcohol on the descending BrAC limb (gs > 0.45 and gs > 0.37, respectively). A moderate magnitude decrease in DSST errors was also observed after AmED relative to alcohol at 0.050% ascending target BrAC (gs > 0.43).

Conclusions: Changes in cognitive function after AmED administration were dependent on the degree of intoxication, BrAC curve limb, and ED volume. Co-administration of ED doses which matched (500 ml) and exceeded (500 ml) maximum daily intake guidelines with alcohol decreased impairment of psychomotor function and global information processing after alcohol consumption. These results cannot be necessarily interpreted to suggest that people are less impaired after AmED, as behavior is the result of coordination of multiple cognitive functions, and reduced impairment on one aspect of cognition may not translate into global improvements.