Adolescence represents the body in revolution. The voice changes. Hair grows where it didn’t before. New infusions of hormones flux inside the body, orchestrating the transformations that prime the body for adulthood and reproduction. But adolescence isn’t confined to the body. Across human cultures, adolescents begin to engage in new “adult” behaviors that shape both the body and mind. From sex and bodily fluids to social rituals laden with alcohol, teens begin engaging in adult behaviors that can have long-lasting effects on their bodies. Shifting the weight of responsibility away from the adolescent, legal codes and social norms establish parameters for action that protect adolescents. For example, in most countries, teens are legally prohibited from drinking alcohol until they turn eighteen thereby protecting teens from possibly damaging their still-developing bodies. Nevertheless, many states have carve-outs allowing minors to drink with parents and/or at home. This is where the social norms kick in.
Caffeine consumption, unlike alcohol consumption, is legally unregulated and mostly governed by unwritten social norms which vary greatly from place to place. In my native homeland of Latin America for example, it is not uncommon for children and teens to be served coffee with milk in their morning meals – the dose controlled by the parent’s measure. Meanwhile, in the U.S., children and teens increasingly consume caffeine in the form of sodas, candies, and other newly-caffeined-enriched foods. Such is the case that daily caffeine consumption amongst 9 to 17 year-old Americans has doubled since 1980 (Frary et al, 2005). Although when used by healthy adults caffeine is considered to be relatively safe, caffeine intake is positively correlated with substance-use disorders, illicit drug use, and other risky behaviors in adolescents (Miller, 2008; Kendler et al, 2006). With new patterns of increased caffeine consumption amongst American children and teens, is it time we reconsider our social norms around caffeine to protect the wellbeing of the next generation?
A recent study by neurobiologists at the University of Colorado Boulder brings new light to this dilemma in demonstrating how caffeine consumption may shape the developing nervous system of adolescents. The researchers subjected one group of rats to caffeine during adolescence, and another to water. Once the rats reached adulthood, the researchers tested the rats’ sensitivity to cocaine, by administering increasing doses of cocaine over four hours and then measuring their physical activity. Although the caffeine-consuming rats were not given caffeine into adulthood, they were more sensitive to the effects of cocaine as adults compared to the control rats. On one behavior test for example, the rats that consumed caffeine as adolescents exhibited greater hyperactivity when given cocaine compared to the control rats. This suggests that caffeine consumption during adolescence can have longstanding effects on brain function even into adulthood (O'Neill et al., 2014). The researchers then characterized these changes in the brain, by implanting a small catheter probe into the brain of the experimental rats, allowing them to sample and measure the concentration of neurotransmitters over time in a live animal. They found that the rats that consumed caffeine as adolescents had a greater increase in dopamine in response to cocaine compared to control rats. Another test known as immunoblotting , showed that not only was there a stronger increase of dopamine quantities in experimental rats, but also increased dopamine and adenosine receptors. These effects on dopamine function are crucial, since dopamine plays a key role in reward, motivation, and decision-making.
Although these experiments were performed in rats and only testing the effects on a few behaviors, the findings suggest that exposure to caffeine during adolescence may have both life-long neurobiological and behavioral consequences – affecting dopamine circuits critical to our sense of motivation and reward. The public should recognize that caffeine, despite its ubiquity and seemingly short-lasting effects, can have life-long consequences on the brain’s motivation and reward systems.
1. Frary CD, Johnson RK, Wang MQ. Food sources and intakes of caffeine in the diets of persons in the United States. J Am Diet Assoc. 2005;105:110–113.
2. Kendler KS, Myers J, O Gardner C. Caffeine intake, toxicity and dependence and lifetime risk for psychiatric and substance use disorders: an epidemiologic and co-twin control analysis. Psychol Med. 2006;36:1717–1725.
3. Miller KE. Energy drinks, race, and problem behaviors among college students. J Adolesc Health. 2008;43:490–497.
4. O'Neill, Casey E, et al. “Effects of Adolescent Caffeine Consumption on Cocaine Sensitivity.” Neuropsychopharmacology, vol. 40, no. 4, 2014, pp. 813–821., doi:10.1038/npp.2014.278.