Effect of Genetic Information and Information About Caffeine Content on Caffeine Withdrawal Symptoms.

This study sought to test the effect of genetic information and information about the caffeine content of a beverage on caffeine withdrawal, specifically if: (1) being informed that one has tested positive for a gene related to caffeine withdrawal can produce an exaggerated caffeine withdrawal response during abstinence; (2) belief that one has consumed caffeine leads to a reduction in withdrawal symptoms when no caffeine is consumed. Regular coffee drinkers were given a bogus genetic test and were told either that they had tested positive or negative for a gene related to withdrawal. After 24-hour caffeine abstinence withdrawal symptoms were measured using a self-report caffeine withdrawal scale, and then again after a cup of decaffeinated coffee. Half the participants were told their coffee was caffeinated and half were told truthfully that it was decaffeinated. Participants told the coffee was caffeinated reported a greater reduction in withdrawal symptoms than those told it was decaffeinated. Differing genetic test result information produced no difference in reported withdrawal symptoms. These results indicate that information about the dose of caffeine administered can influence withdrawal symptoms, but that genetic information does not have a universal ability to produce nocebo effects across all sensory and cognitive domains.