The Cognitive and Subjective Effects of Chronic Caffeinated Energy Drink Consumption in Young Adults

Caffeinated beverages, including energy drinks (EDs), are widely consumed for their purported cognitive enhancing effects. Most prior research studies on the cognitive effects of caffeine have examined acute effects; however, caffeine is most often consumed in a chronic fashion. Furthermore, chronic caffeine consumption can produce tolerance and physical dependence, which manifests as cognitive and emotional disruptions upon acute abstinence. The present study investigated the attentional and subjective effects of caffeinated EDs consumed daily for three weeks. It has been proposed that attention can be divided into three networks—alerting, orienting and executive control (Posner & Peterson, 1990), which are often assessed with the Attention Network Task (ANT; Fan et al., 2002). Thirty-seven light non-dependent caffeine consumers (43.2% female; mean daily caffeine use = 81.26 mg) participated in a six week within-subjects study. After a one-week baseline period, participants consumed one week of daily placebo EDs, followed by three weeks of daily caffeinated EDs (200 mg), and then one week of daily placebo EDs. Reactions to the EDs were assessed in the laboratory across nine different timepoints. Consumption of caffeinated EDs (timepoints 4, 5, and 6) produced faster reaction times (RTs) but no differences for percent error and the three attention networks compared to placebo EDs (timepoints 3, 7, and 8). Acute caffeinated ED exposure (timepoint 4) produced faster RTs and improvements in executive control than the placebo ED (timepoint 3), but no differences for percent error or the alerting and orienting networks. Greater mood disturbances and withdrawal symptoms were observed in response to the placebo ED (timepoints 7 or 8; 24 and 48 hours of abstinence, respectively) that was consumed after three weeks of daily caffeinated EDs when compared to the placebo ED that was consumed prior to caffeine exposure (timepoint 3). The unexpected effects of caffeine and acute caffeine abstinence on ANT performance warrant future inquiry. The findings from the present study suggest that physical dependence develops after only three weeks of daily moderate caffeine exposure and have implications for the use of caffeinated EDs for cognitive enhancement.