Caffeine in children’s soft drinks linked to shorter sleep and brain differences

A study of more than 9,600 children found that higher caffeine intake, mainly from soft drinks, was associated with shorter sleep, subtle differences in brain structure and later mental health difficulties, although it cannot prove cause and effect.

Children who drink more caffeine, mostly through soft drinks, appear to sleep less and show small but measurable differences in brain structure, according to researchers at King’s College London. The study looked at 9,632 children aged nine to 11 taking part in the Adolescent Brain Cognitive Development study and found that higher caffeine intake was tied to a slightly smaller cortical surface area, the folded outer layer of the brain involved in attention, memory, decision-making and emotional control.

The association was visible even at relatively low levels of intake. Researchers reported that differences in overall brain surface area were linked to consumption as low as one caffeinated drink a week, compared with none. The effect was seen across 22 brain regions spanning all four lobes, and it remained after the team accounted for family background, including household income and parents’ educational level. Related summaries of the peer-reviewed paper say soft drinks were the main source of caffeine in the children’s diets.

The findings do not prove that caffeine caused the brain differences, and the researchers cautioned against reading the results as evidence of direct harm from a single drink each week. Still, the pattern is notable because caffeine is a stimulant that can delay or disrupt sleep, especially when taken later in the day. In this study, children who consumed more caffeine tended to sleep for shorter periods, and shorter sleep was also associated with differences in cortical surface area.

That sleep link mattered beyond brain scans. The researchers found that shorter sleep and lower cortical surface area helped explain why higher caffeine intake was connected to more mental health problems six months later, including difficulties with attention, mood and behaviour. When the children were assessed again 18 months later, the relationship between caffeine intake and later mental health still appeared to run through brain structure, although the sleep pathway was no longer evident.

The study adds to growing concern about how much caffeine children consume without parents fully realising it. The researchers said caffeine has become so routine that families may underestimate how much young people are getting, particularly from soft drinks. They called for further work to pin down what children are drinking, how much caffeine those drinks contain and when they are consumed, while also urging parents to check labels, encourage water and other caffeine-free alternatives, and support regular bedtime routines.