Every generation grows weaker and wiser

Afraid of coffee?

Coffee is and will remain the favorite drink of Germans. According to the German Coffee Association, they drank 1.3 billion cups last year. In other words: on average, every German enjoyed 150 liters of coffee over the year.

What makes drinks such as coffee and tea, but also cola and cocoa so popular around the world, is above all their stimulating effect. However, this causes problems for other people: After consuming caffeinated drinks, they experience palpitations, sweats, restlessness and difficulty falling asleep; many of them also experience a vague fear. Because of this, patients who suffer from anxiety disorders often stop drinking coffee or reduce their consumption.

Scientists from Würzburg under the direction of the psychiatrist Professor Jürgen Deckert and a working group led by Peter Rogers from the University of Bristol have now found out that the extent of anxiety also depends on the regularity of coffee consumption. The journal Neuropsychopharmacology reports on their work in its latest issue.

Changes in the genome are the trigger

Changes in the genome are responsible for the fact that some people react with fear to a cup of coffee or tea. “We were able to show that a variant in the gene for the adenosine A2A receptor plays an important role in this process,” says Jürgen Deckert. The messenger substance adenosine normally docks with this receptor in certain areas of the brain and thus triggers a calming reaction. If the receptor gene is changed, however, caffeine can displace adenosine and thus prevent its calming effect.

To do this, however, those affected have to carry the changed gene on both the paternal and maternal chromosomes. “In a study on volunteers in cooperation with Harriet de Wit's working group from the University of Chicago, we found that only those subjects who had the same gene variants on the long arm of both chromosomes 22 were exposed to a medium dose of caffeine Fear reacted, ”says Deckert. Like the stimulant effects of caffeine, this effect was temporary; over time it subsided and was completely gone after a few hours.

It all depends on the dose

The fear reaction only occurred when the test subjects consumed a medium dose of caffeine - namely 150 milligrams, which corresponds to about two cups of coffee. At a lower dose (50 milligrams) none of the test subjects reacted with fear, at a high dose (400 milligrams), on the other hand, all test subjects showed increased anxiety - according to the result of a further study with scientists from the University of Chicago. The genetic variation is only relevant for the development of anxiety in the medium dose range.

“The result is not surprising. You can find similar trends in other areas, ”says Deckert. An example: Normally no viewer is afraid of a romance film, whereas everyone is afraid of a horror film. With the “medium dose” - a crime thriller - only those who are sensitive to it feel fear.

Regular consumption makes you insensitive

However, anyone who reacts to coffee with fear does not have to do so for the rest of their life. “In our most recent study, together with Peter Rogers from the University of Bristol, we looked into the question of whether the level of daily caffeine consumption of the test subjects had an effect on the gene effect,” says Deckert. The results showed that the gene effect is weaker in people who regularly consumed a medium or high dose of caffeine. In other words: "The genetic intolerance can probably recede with a gradual increase in the dose and regular consumption," says the doctor. Deckert sees the results of these studies as further evidence of how complex gene-environment interactions can be.

The connection with anxiety disorders

A few years ago, the Würzburg researchers, in collaboration with researchers at the University of Bonn led by Markus Nöthen, identified the same genetic variant that leads to increased anxiety after consuming caffeine as a genetic risk variant for anxiety disorders. However, it cannot alone be the cause of an anxiety disorder. "Here, additional environmental factors such as the consumption of caffeine or traumatic life events are certainly needed," says Jürgen Deckert.

Test subjects wanted

These complex interactions between caffeine and other substances that have an indirect effect on the adenosine A2A receptor are currently being investigated by the Würzburg researchers in cooperation with a Münster research group led by Katharina Domschke as part of the Collaborative Research Center SFB TRR 58 “Fear, Anxiety, Anxiety Diseases”. We are still looking for volunteer participants. The subjects should be healthy and between 18 and 65 years old. If you are interested, you can contact us at T: (0931) 312687 or email: [email protected] "

Association of the Anxiogenic and Alerting Effects of Caffeine with ADORA2A and ADORA1 Polymorphisms and Habitual Level of Caffeine Consumption ”, Peter J Rogers, Christa Hohoff, Susan V Heatherley, Emma L Mullings, Peter J Maxfield, Richard P Evershed, Jürgen Deckert and David J Nutt. Neuropsychopharmacology (2010) 35, 1973-1983, doi: 10.1038 / npp.2010.71

Contact: Prof. Dr. Jürgen Deckert, Clinic and Polyclinic for Psychiatry, Psychosomatics and Psychotherapy, T: (0931) 201 77 000, E-Mail: [email protected]

By Gunnar Bartsch