Alcohol consumption of people who consume alcohol mixed with energy drink: Meta-analyses of between-group studies and within-subject comparisons

Purpose: There is debate about whether consuming alcohol mixed with energy drink (AMED) increases overall alcohol consumption. The aim of this study was to conduct meta-analyses on data from studies using a between-group design (i.e., comparing alcohol consumption of AMED consumers with alcohol consumption of people who consume alcohol only) and within-subject design (i.e., comparing within AMED consumers alcohol consumption on AMED occasions with other occasions on which they consume alcohol only). Methods: A literature search (PubMed, Embase, PsycINFO) was conducted to identify studies applying a between-group and/or within-subject design, and provided sufficient information on alcohol consumption to enable inclusion in a meta-analysis. Meta-analyses were conducted separately for studies with a between-group design and within-subject design. Results: Eleven studies applying a between-group design and 8 studies applying a within-subject design were included, comprising data from Brazil, Canada, the USA, Australia and the Netherlands. The between-group design meta-analysis revealed that AMED consumers (N = 5,335) consume significantly more alcohol on a drinking occasion than alcohol only consumers, i.e., people who consume alcohol but not AMED (N = 14,310): ES = 1.257, 95%CI = 0.474-2.040; p = 0.002). The within-subject design meta-analysis among AMED consumers (N = 3,302) revealed no significant difference between total alcohol consumption on AMED occasions when compared to alcohol only occasions: ES = -0.020, 95%CI = -0.142 to 0.102; p = 0.750. Conclusion: AMED consumers consume significantly more alcohol than people who consume alcohol only. However, within-subject comparisons show that they consume the same amount of alcohol on occasions when they consume AMED or alcohol only. In other words, mixing alcohol with energy drink does not increase their total alcohol consumption. Other moderating variables (i.e., differences in personality) may explain the observed difference in alcohol consumption of AMED consumers and people who consume alcohol only.