Young people who consume more caffeine, mostly from soft drinks, sleep less and show small differences in how their brains are developing, according to a study led by researchers at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King's College London.
The researchers drew on data from 9,632 children aged nine to eleven taking part in the Adolescent Brain Cognitive Development (ABCD) Study, which follows the brain development and health of young people across the US. Each child said how many caffeinated drinks they usually had in a week, whether coffee, tea or soft drinks, with parents reporting how long the children usually sleep on average. MRI scans then measured thickness and surface area of the cortex, the brain's folded outer layer, which plays a part in cognitive processing, decision making, attention and emotions, among other important functions.
The children were then asked to report back on their mental health 6 and 18 months later with the results showing that greater caffeine consumption is associated with lower surface area across the cortex, even after we adjust for household socioeconomic circumstances like parental educational attainment and income. The pattern showed up in 22 separate regions, spanning all four lobes of the brain. These effects were largely driven by the consumption of soft drinks, which were the biggest source of caffeine in the study. Differences in overall surface area showed up from as little as one caffeinated drink a week, compared with none.
Caffeine is such a normal part of daily life that it's easy to forget young people are consuming it too. Studies have found that two-thirds of adolescents consume caffeine at least once a week. Despite it being a psychoactive substance, it is completely unregulated.
Dr Divyangana Rakesh, Senior Lecturer in Neuroscience and Psychology and senior author of the study from the IoPPN at King's College London.
"We found that even fairly low levels of intake were linked to small differences in brain structure and later mental health, and lower sleep duration seems to be an important underlying link. Although we cannot comment on causality, our results do suggest that both caffeine intake, including from soft drinks, and sleep are worth paying attention to when we think about young people's mental health," commented Dr Divyangana Rakesh, Senior Lecturer in Neuroscience and Psychology and senior author of the study.
The researchers then looked at what might connect caffeine to differences in brain structure. Young people who consumed more caffeine slept less, which was in turn linked to lower surface area. Together, shorter sleep and lower surface area partly explained the link between higher caffeine intake and more mental health problems six months later, including problems with attention, mood and behaviour. At 18 months, only the link through overall surface area was still there.
Soft drinks contain a lot of sugar and often go hand in hand with less healthy lifestyle habits and more risk-taking behaviours, so we can't yet separate the role of caffeine from everything else that comes with them. That's the next question we want to answer, ideally with more precise measures of what young people drink, when they drink it and how well they sleep.
Jiayi Zheng, first author of the study from the IoPPN at King's College London.
Zheng J, Rakesh D. Caffeine Consumption and Adolescent Mental Health: The Role of Sleep and Brain Structure was published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. DOI: 10.1016/j.bpsc.2026.09.011
Dr Divyangana Rakesh is supported by a Young Investigator Grant from the Brain & Behavior Research Foundation, a New Investigator Research Grant from the UKRI Medical Research Council and the CIFAR Global Scholars Program. The ABCD Study is supported by the US National Institutes of Health and additional federal partners.
