Caffeine isn't just something adults get from their morning coffee. Children consume it too, often through everyday soft drinks, and new research suggests those habits may be connected to how much they sleep and subtle differences in their developing brains.
A study of 9,632 American children ages 9 to 11 found that those who consumed more caffeine tended to sleep less and showed small differences in brain structure. Researchers also found a connection with mental health symptoms reported months later. The findings, published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, don't establish that caffeine caused any of these differences.
"Caffeine is such a normal part of daily life that it's easy to forget young people are consuming it too," said Divyangana Rakesh, the study's senior author and a researcher at King's College London.
Researchers examined children's usual consumption of caffeinated soft drinks, coffee and tea, along with information from parents about their children's sleep. They also used brain scans to look for differences in the brain's outer layer, which is involved in attention, decision-making and emotions.
Children who consumed more caffeine generally slept less and had slightly less surface area across parts of this outer layer. The findings were largely associated with soft drink consumption, the biggest source of caffeine among participants.
The differences appeared even among children who reported having as little as one caffeinated drink per week compared with none. However, the changes were small, and the study doesn't show that an occasional soda harms brain development.
Researchers also explored whether sleep might help explain the findings. Shorter sleep was linked to the brain differences, and the combination was associated with slightly more reported problems involving attention, mood and behavior six months later. Some of these associations were still present at 18 months.
That connection is worth investigating because sleep plays an important role in children's development, and caffeine is already known to interfere with sleep. What's less clear is whether the brain differences identified in this study have any lasting consequences.
It's also difficult to know how much of the association comes from caffeine itself. Soft drinks often contain sugar, and children who drink more of them may have different eating habits, sleep routines or other lifestyle factors that could influence the results.
"Soft drinks contain a lot of sugar and often go hand in hand with less healthy lifestyle habits and more risk-taking behaviors, so we can't yet separate the role of caffeine from everything else that comes with them," said Jiayi Zheng, the study's first author.
There are other uncertainties, too. Children reported how many caffeinated drinks they typically consumed, while parents estimated how long they slept. Those estimates may not be entirely accurate, and the study didn't measure exactly how much caffeine children consumed. Researchers also couldn't determine whether caffeine use preceded the differences seen on brain scans.
The findings offer another reason for parents to pay attention to caffeine in children's drinks, particularly if sleep is a concern. But they don't establish that drinking caffeine causes brain damage or mental health problems. More research is needed to understand whether caffeine, sleep habits or other factors are responsible for the relationships observed.
The research received support from the Brain & Behavior Research Foundation, the United Kingdom's Medical Research Council and the CIFAR Global Scholars Program. Data came from the Adolescent Brain Cognitive Development Study, supported by the U.S. National Institutes of Health and other federal partners.