Effects of Adolescent Caffeine Consumption on Anxiety and Stress in Adulthood

Caffeine is the most widely used psychoactive substance in the world. Although adolescents are the most rapidly increasing group of caffeine consumers, few studies have been done on the effects of caffeine on the still-developing adolescent brain. Since caffeine has been associated with stress reactivity and anxiety behavior, this study examined the effect of adolescent caffeine consumption on these measures in adulthood using a rat model. Male Sprague Dawley rats were exposed to caffeine (0.3 g/L) for the duration of their adolescence (postnatal days 28-56). Once they were adults and had withdrawn from caffeine for a week (after postnatal day 60), they were exposed to either an elevated plus maze to measure anxiety behavior, or underwent a pedestal stress test. From the pedestal stress test, in situ hybridization was used to measure c-fos mRNA in the basolateral amygdala (BLA), paraventricular nucleus (PVN), and bed nucleus of the stria terminalis (BST), and immunoassays were performed to determine corticosterone (CORT) levels in the blood plasma. Animals that consumed caffeine in their adolescence spent significantly less time in the open arms of the elevated plus maze in adulthood, indicating heightened anxiety. Accordingly, animals that consumed caffeine in their adolescence had heightened BLA activity in response to the pedestal stress. These animals also as adults displayed higher basal CORT levels and blunted CORT levels in response to a stressor, implying a dysregulation of their stress response system. PVN activity was higher basally, potentially explaining the rise in basal CORT release. The BST activity had no significant results. Although it is unclear how caffeine is causing these changes in behavior, neuronal activity and neuroendocrine measures, it is apparent that the consumption of caffeine in adolescence can have persistent unwanted effects on anxiety behavior and stress reactivity in adulthood. EFFECTS OF CAFFEINE ON ANXIETY AND STRESS 3