Does drinking coffee at night make us more impulsive and reckless?

The study was conducted at the Department of Biology at the University of Texas at El Paso (UTEP), USA and published in the journal iScience. The research team used fruit flies (Drosophila melanogaster), a species commonly used in behavioral research due to their genetic and neurological structure similar to humans, to test the effects of coffee when consumed at night.

"Caffeine is the most widely consumed psychoactive substance in the world , with approximately 85% of adults in the United States using it regularly," said researcher Paul Sabandal, a professor in the UTEP department of biology. "We wanted to understand whether there were factors that caused caffeine to affect behavior differently."

In a series of experiments, the researchers fed flies diets containing caffeine at varying doses, distinguishing between daytime and nighttime intake, with or without sleep deprivation.

The results showed that flies given caffeine at night tended to react more impulsively. Specifically, they were less likely to stop moving when faced with a strong wind gust, a natural irritant, and continued flying around wildly.

"Normally, flies will stop flying when they encounter strong winds. But when they are given caffeine at night, they fly recklessly, despite the discomfort," researcher Erick Saldes shared.

In contrast, when caffeine was consumed during the day, this abnormal behavior did not appear.

Notably, the study also found a clear difference between the sexes: despite similar levels of caffeine in their bodies, female flies exhibited more impulsive behavior than male flies.

"Flies don't have hormones like humans, like estrogen. This suggests there may be other genetic or physiological factors that make females more sensitive to caffeine," explains Professor Kyung-An Han.

Although the study was conducted on fruit flies, experts say the results still have important implications for humans.

The fruit fly (Drosophila melanogaster) is a popular biological model for neuroscience research because it shares many similarities with humans in terms of genetic structure and neural responses. Behaviors such as learning, memory, and response to stimuli can all be studied in this species.

Thus, the fact that fruit flies exhibit impulsive behavior after nocturnal caffeine consumption suggests the possibility of a similar response in humans, especially in situations of sleep deprivation or night shift work.