October 15, 2026

expert reaction to observational study on caffeine consumption in adolescents, sleep and brain structure

Scientists comment on an observational study, published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, investigating caffeine consumption in adolescents, sleep and brain structure. 

Prof Derek Hill, Professor of Digital Health, UCL, said:

“The authors have data from nearly 10,000 children aged 9-11, and examine the relationship between caffeine intake, brain structure, sleep, and subsequent mental health outcomes. While this is an interesting topic to investigate, the study design has significant limitations and care must be taken in interpreting the conclusions.   It is widely understood that caffeine intake has an impact on sleep. The more innovative aspect of this paper is to look at the association between caffeine intake, sleep, brain structure and subsequent mental health support.   The authors propose that there is an association between caffeine intake and certain aspects of brain structure and sleep, and that sleep and brain structure may mediate the link between caffeine intake and mental health outcomes. But very low confidence must be associated with this finding because:

(1) the brain imaging is only at a single timepoint – there is no measure of how an individual’s brain changes as a result of caffeine 

(2) the measure of sleep is a questionnaire completed by the parents, which is often unreliable, as parents may not make good estimates of their child’s sleep, and can’t pick up any of the more subtle sleep disturbance and sleep architecture changes that are biologically important 

(3) the authors do not link their findings to dose of caffeine nor timing of dose (which is well known to impact caffeine effect on sleep)

(4) the mental health outcomes were self-reported by the young people, rather than linked to any assessment by a health care professional. 

“The methodology is therefore limited in its ability to answer the question as to whether the effect of caffeine on mental health outcomes is mediated by sleep and brain structure changes. There is a risk that the findings reported arise purely from chance and are a consequence of the limitations of their data. Even if their associations are real, the design is not a good way of showing causality, and the biological or medical significance of their finding is not clear. The conclusions of the paper should be considered speculative.”

Dr Charalampos Rallis, Reader in Genetics, Genomics and Fundamental Cell Biology at Queen Mary University of London said:

“This is a large, well-conducted study, but its observational design cannot establish that caffeine causes changes in children’s brains. The study measured caffeine intake, sleep, and brain structure at the same time point, and the observed brain differences are very small. The association with later mental health is negligible. The findings were driven largely by soft drinks. However, sugar intake, diet, and broader lifestyle factors may also contribute. The most robust conclusion is consistent with existing evidence: caffeine can reduce sleep in children.”

‘Caffeine Consumption and Adolescent Mental Health: The Role of Sleep and Brain Structure’ by Zheng J et al. was published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging at 14:00 UK time on Thursday 15 October.

DOI: 10.1016/j.bpsc.2026.09.011 

Declared interests

Prof Derek Hill: Derek Hill has no conflicts of interest related to this work. He receives funding from pharmaceutical companies for his research at UCL, and is founder of a company that works on assessing safety and effectiveness of novel treatments. 

Dr Charalampos Rallis: Dr Rallis has no industry or financial interests to declare.