Sex differences in reinforcing value of caffeinated beverages in adolescents.

Caffeine use is increasing among children and adolescents, but the effects of caffeine use on behavior and physiology within this population remain understudied and poorly understood. The purpose of this study was to test the hypothesis that adolescents find caffeinated soda more reinforcing than noncaffeinated soda and that this would be related to the level of usual caffeine consumption and to sex. We measured operant responding for portions of caffeinated and noncaffeinated soda at baseline and after daily consumption of 32 oz of caffeinated and noncaffeinated soda for 1 week each in 12-17-year-old participants. Participants also completed a behavioral checklist, a beverage-liking questionnaire, and a 24-h dietary recall to assess the energy intake at baseline and again after each week of beverage consumption. There was no difference in reinforcing value of noncaffeinated or caffeinated soda as a function of usual caffeine consumption. However, males found the caffeinated soda significantly more reinforcing than did females after the exposure period. To our knowledge, this is the first study to show a sex difference in the reinforcing value of caffeinated soda. These data suggest that boys may be more susceptible to the reinforcing effects of caffeine.