Coffee, the most widely used psychostimulant in the world, is debated. It would be good for your health (see Should you drink coffee?), or responsible for disorders. What is certain is that it prevents sleep, because it contains caffeine, whose waking properties are manifested by blocking adenosine receptors, which promote sleep.
A new American study shows that coffee is more than just a stimulant, and that it disrupts our circadian cycle, normally regulated by light. Our internal clock is set on a 24-hour cycle, and it signals when to sleep and when to wake up depending on the light.
In this study published in the journal Science Translational Medicine , the researchers observed that people who took caffeine in low light had a 40-minute shift in their day-night rhythm compared to those who took a placebo in the same light conditions. These results therefore explain why those who drink coffee at night fall asleep and wake up later.
