Nighttime Coffee Consumption Linked to Increased Impulsive Behavior in Women, Study Finds

A recent study from the University of Texas at El Paso (UTEP) has revealed that drinking coffee at night may increase impulsive behavior, particularly in women. Published in the journal iScience, the research used fruit flies (Drosophila melanogaster) to explore caffeine’s effects on behavior, capitalizing on their genetic and neural similarities to humans.

The study introduced caffeine into the flies’ diets under varied conditions—different doses, daytime versus nighttime consumption, and combinations with sleep deprivation. To measure impulsivity, the flies were exposed to strong airflow, a stimulus that normally causes them to stop moving. However, flies that consumed caffeine at night showed a reduced ability to suppress movement, flying recklessly despite the unpleasant conditions. In contrast, flies that consumed caffeine during the day did not exhibit such impulsive behavior.

Notably, female flies were more susceptible to caffeine-induced impulsivity than males, even though both had comparable caffeine levels in their bodies. Since fruit flies lack human hormones like estrogen, the researchers suspect other genetic or physiological factors contribute to this heightened sensitivity in females. Understanding these mechanisms could shed light on how nighttime physiology and sex-specific dynamics influence caffeine’s effects.

These findings raise concerns for people who consume caffeine at night to stay alert—such as shift workers, healthcare staff, and military personnel—where impulsive behavior could lead to risky decisions. The study highlights that the timing of caffeine intake is important; late-night coffee might not only disrupt sleep but also affect decision-making and behavior.

Disclaimer: This study was conducted using fruit fly models, which provide insights into human biology but do not perfectly replicate human responses. Further research is necessary to confirm whether these findings translate directly to humans. Individuals should consider their own health conditions and consult healthcare professionals regarding caffeine consumption.