Your (fake) morning brew: Placebo reduces caffeine withdrawal in abstinent coffee drinkers

When you can’t get your morning coffee, you’re cranky, irritated, drowsy, irritable, and can’t concentrate. These withdrawal symptoms have been widely tested and confirmed through numerous studies. Other studies have yielded that information about caffeine content of a beverage (regardless of its accuracy) increase positive effects of alertness, contentedness, and calmness.

A new study, published in the Journal of Psychopharmacology, aimed to examine if the negative effects of caffeine withdrawal, such as crankiness, could be reversed by information about the beverage caffeine content.

Researchers recruited 89 participants between the ages of 18 and 45 years old, most of whom were female. The researchers incorporated different factors when designing their experiment. The first was priming (or not priming) the participants. When participants are primed, they are exposed to one stimulus, which affects their responses to another stimulus. In this case, the participants were either “given information suggesting abstaining from caffeine could lead to substantial withdrawal symptoms… or they were not given this information” through an email preparing them for the study the next day.

Participants abstained from caffeine for 24 hours. Upon arrival, researchers collected saliva samples and blood pressure readings. Then, participants answered questions concerning their caffeine withdrawal symptoms. The next factor was expectancy; participants were given decaf coffee and either told that it was caffeinated or told it was decaffeinated. The coffee used in the study was, in fact, decaffeinated. After the coffee, participants again answers questions about their caffeine withdrawal symptoms.

The results of the study show that caffeine withdrawal symptoms can be reduced by the belief that caffeine has been ingested, even when it has not. Participants who believed they were receiving caffeinated coffee showed a greater reduction of withdrawal symptoms. Four specific types of withdrawal symptoms were reducible by expecting coffee: flu-like symptoms, craving, difficulty concentrating, and drowsiness. Researchers commented that this suggests that the belief that one has ingested caffeine lowers withdrawal symptoms but also the motivation to consume caffeine. The study also found that the withdrawal reduction effect lasted for around 45 minutes and is longer than placebo-induced alertness, which is closer to 15-20 minutes.

There were some important limitations to the current study. The most important was that there was no definitive way to test that participants had not ingested caffeine for 24 hours. Instead, this measure relied on the participants reporting it themselves. Another limitation to consider is that the study was single-blind only, meaning that the participants did not know if the coffee was caffeinated or not, but the researchers did. A more effective study in the future might make this aspect of the study double blind, and also have an objective way to measure caffeine abstinence.

Finally, this study suggests “expectancy-based interventions designed to reduce or eliminate drug intake may serve as a useful adjunct to existing interventions, both for caffeine use specifically, and for other substance use disorders.”