The effect of chronic energy drink consumption on cognitive and behavioral responses in laboratory rodents

BACKGROUND: Energy drinks formulated to enhance mental and physical performance have been shown to induce dependence and withdrawal symptoms.

AIM: The study aimed to investigate the effects of chronic energy drink consumption on cognitive function and behavior in laboratory rodents.

METHODS: The study examined the effects of energy drinks (containing 30 mg and 200 mg of caffeine per 100 mL) administered intragastrically (0.5 mL for rats and 0.2 mL for mice) for 28 days. A total of 72 outbred SD male rats were tested using the Passive Avoidance Conditioning test and the Extrapolation Escape test, whereas 72 outbred CD1 male mice were evaluated in the Open Field and Social Behavior tests. Control animals received water in equivalent volumes, whereas experimental groups were administered energy drinks with varying caffeine concentrations. The statistical analysis was performed using SPSS (version 17.0) software, applying the Kolmogorov–Smirnov test, Wilcoxon signed-rank test, and Mann–Whitney U test. Results were considered statistically significant at p ≤ 0.05.

RESULTS: The low-caffeine energy drink impaired memory retention in the Passive Avoidance Conditioning test on days 21 and 28 (p = 0.045; p = 0.050, respectively) and increased response latency in the Extrapolation Escape test at later observation periods due to delayed motor activity, diving latency, and grid detection latency on day 14 (p = 0.002), day 21 (p = 0.003; p = 0.002; p = 0.002, respectively), and day 28 (p = 0.004; p = 0.002; p = 0.002, respectively). The high-caffeine energy drink reduced conditioned reflex formation in the Passive Avoidance Conditioning test on days 14, 21, and 28 (p = 0.050; p = 0.016; p = 0.009, respectively) and prolonged decision-making in the hierarchical task on days 14–28, increasing the latency for motor activity (p = 0.002), diving (p = 0.002), and grid detection (p = 0.002). Exploratory behavior in mice followed a wave-like pattern under the influence of energy drinks. Consumption of the low-caffeine energy drink was associated with increased horizontal activity and burrowing behavior during the early observation period (days 7–14, p = 0.002), followed by a decline at later stages (days 21–28, horizontal activity, p = 0.040; burrowing reflex, p = 0.009). A similar trend in horizontal activity was observed with the high-caffeine energy drink (days 7–28, p = 0.002). However, burrowing behavior was significantly reduced on days 21–28 (p = 0.003, p = 0.002, respectively). Increased anxiety reflected by prolonged freezing behavior was observed in mice consuming the high-caffeine energy drink on days 14–28 (p = 0.002; p = 0.002; p = 0.001, respectively). Frequent but brief grooming in mice consuming the low-caffeine energy drink also indicated heightened anxiety (day 14, p = 0.003; day 28, p = 0.005). Increased aggression was recorded in mice exposed to the low-caffeine energy drink on days 14–28 (p = 0.045; p = 0.002; p = 0.002, respectively), whereas persistent aggression was observed throughout the entire observation period in the high-caffeine energy drink group (p = 0.011; p = 0.002; p = 0.002; p = 0.002, respectively).

CONCLUSION: Chronic consumption of energy drinks (30 mg and 200 mg of caffeine per 100 mL for 28 days) does not enhance cognitive abilities and leads to impaired behavioral responses in rodents.