Caffeine intake in children was linked to less sleep and small brain-structure differences

Researchers used data from 9,632 U.S. children ages 9 to 11 who were taking part in the Adolescent Brain Cognitive Development Study. The study follows young people’s brain development and health over time.

The children reported their usual intake of caffeinated drinks, including coffee, tea, and soft drinks. They also reported on mental health. Parents reported the children’s average sleep duration. Researchers used MRI, a scan that creates detailed pictures of the brain, to measure the thickness and surface area of the cortex. The cortex is the brain’s folded outer layer.

The main finding was an association: children reporting higher total caffeine intake tended to have lower total cortical surface area. The study estimated this relationship as B=-0.03, with a standard error of 0.01 and a p value of .001. These statistics indicate that the pattern was unlikely to be explained by random variation in this data set, but they do not show that caffeine was the cause.

Lower surface area was reported in 22 regions across the brain’s four lobes. According to the study abstract, soft drinks largely drove these findings. There were also some additional links between coffee and espresso intake and cortical thickness, which is a different brain measurement.

The associations were evident at reported intake levels as low as one cup per week. That comparison does not mean one drink a week changes a child’s brain. It means the researchers observed differences between groups with different reported intake levels. The study does not provide evidence that reducing or avoiding a particular drink would produce a particular change.

The researchers also examined sleep as a possible part of the pattern. Higher caffeine intake was linked with shorter sleep duration, and shorter sleep was linked with lower cortical surface area. In a statistical analysis designed to explore possible pathways, shorter sleep followed by lower surface area partly explained the association between greater caffeine intake and greater mental health problems reported at six months and 18 months.

“Mediated” or “partly explained” has a specific meaning here. It describes a pattern in the data that is consistent with sleep and brain structure being part of the link. It does not prove a chain of events in which caffeine led to less sleep, then changed the brain, then caused mental health problems.

The research team used linear mixed-effects models to test links between caffeine intake and brain measures. They used structural equation modeling, another statistical approach, to examine the possible roles of sleep duration and brain structure in later mental health reports.

This was not a trial in which researchers assigned children to consume caffeine or avoid it. That is important because children who drink more soft drinks may differ in many ways from those who do not. The news coverage notes that soft drinks contain sugar and may occur alongside other lifestyle habits or risk-taking behaviors. Those factors could help explain some or all of the observed associations.

The supplied material also does not provide full details on effect sizes for every brain region, how caffeine and sleep reports were validated, or every factor included in the analyses. Caffeine intake and mental health were based on children’s self-reports, while sleep duration was reported by parents.

The findings add to questions about caffeine use during a period of brain development. More research would need to separate caffeine from sugar, drink type, sleep habits, and other connected behaviors. Studies that track changes over longer periods and measure intake and sleep more directly could help clarify what is driving the links seen here.