Anxious About Coffee?

Photo: Human brain

When people feel anxious after drin-
king coffee, it is often their genes that
are responsible. But in regular coffee
or tea drinkers this effect is reduced;
© Gunnar Bartsch

Not everyone can tolerate coffee; in some people the caffeine can even trigger symptoms of anxiety. This is down to a small variant in their genetic make-up. Its effect can however be mitigated through regular coffee consumption.

What makes drinks such as coffee and tea so popular worldwide is their stimulating effect. But it is an effect that causes discomfort in other people: after having drinks containing caffeine they feel their heart racing, break out in a sweat, feel restless, and have trouble going to sleep; many of them also experience anxiety for no specific reason.

Alterations in genetic make-up are the reason why some people react anxiously to a cup of coffee or tea. “We managed to show that a variant in the gene of the adenosine A2A receptor plays a key role in this process,” says Deckert. Normally, the transmitter adenosine docks onto this receptor in certain areas of the brain, triggering a relaxing response. However, if the receptor gene has been altered, caffeine can displace the adenosine and thereby prevent its relaxing effect.

However, for this to happen, persons affected must carry the altered gene on both their father’s and their mother’s chromosome. “In a study on volunteers in collaboration with Harriet de Wit’s team from the University of Chicago, we established that only those subjects who possessed the same gene variants on the long arm of both chromosomes 22 reacted with anxiety to an average dose of caffeine,” says Deckert. This effect, like the stimulating effect of caffeine, was temporary.

The anxious response only occurred, however, when the subjects consumed an average dose of caffeine – namely 150 milligrams, which equates to roughly two cups of coffee. With a lower dose (50 milligrams) none of the subjects reacted with anxiety, whereas with a higher dose (400 milligrams) every single one of them demonstrated elevated anxiousness – according to the findings of a further study. The genetic variation is therefore only relevant for the development of anxiety when the dose is in the average range.

But people who react anxiously to coffee do not have to do so for the rest of their lives. “In our latest study together with Peter Rogers from the University of Bristol, we explored the issue of whether the level of daily coffee consumption by the subjects has an impact on the gene effect,” says Deckert. It emerged that the gene effect is less pronounced in people who regularly consume an average or high dose of caffeine.; Source: Julius-Maximilians-Universität Würzburg