UC Davis links sleep to adolescent success

UC Davis Health said on August 4 that a new study found sleep quality was more strongly linked than screen time, exercise or diet to how well adolescents did in school and with peers. The research, published in *Psychological Medicine*, examined children ages 10 to 13 and tracked how lifestyle factors related to academic functioning and social problems. UC Davis said the pattern was especially pronounced among young people with anxiety, depression or other mental health challenges. ### Which adolescents did the study examine? The study used data from the Adolescent Brain Cognitive Development, or ABCD, Study, according to UC Davis Health. Researchers looked at four lifestyle factors — sleep quality, screen time, physical activity and diet — and tested how they related to academic functioning and social problems in early adolescence. (health.ucdavis.edu) Children ages 10 to 13 were the focus of the analysis, UC Davis said. The paper described the work as an examination of whether those lifestyle factors mediated links between mental health symptoms and later functional outcomes, including grades and peer difficulties. (health.ucdavis.edu) ### What did the researchers find about sleep versus screens, exercise and diet? Sleep was the strongest lifestyle factor associated with better grades and fewer social problems, UC Davis said. Screen time ranked second, while physical activity and diet were less strongly linked in this analysis. (health.ucdavis.edu) For academic functioning, the paper said sleep quality mediated 18.5% of the relationship with depression, 36.3% with anxiety and 8.3% with psychotic-like experience distress. For social problems, the Cambridge summary said only sleep quality showed mediation above 3%, at 19.6% to 23.3%, while screen time was the second-strongest factor overall. (health.ucdavis.edu) ### Who said the result stood out? Jason Smucny, the study’s first author and a computational neuroscientist in the UC Davis Department of Psychiatry and Behavioral Sciences, said the strength of the sleep finding was unexpected. He said the team expected sleep to matter, but not to separate itself so clearly from the other lifestyle factors, particularly screen time. (health.ucdavis.edu) Tara Niendam, the senior author and executive director of the UC Davis Early Psychosis Programs, said families and clinicians often focus on symptoms such as anxiety and depression, while the daily effects on school and friendships can matter most to adolescents and parents. She said the study suggests sleep may be one pathway connecting mental health symptoms to those real-world outcomes. (health.ucdavis.edu) ### Why did the paper focus on functioning, not only symptoms? UC Davis said adolescence is a period when mental health concerns often emerge. The health system cited global estimates that about one in seven adolescents experiences a mental disorder, with depression and anxiety among the leading causes of illness and disability in young people. (health.ucdavis.edu) The researchers framed the question around functioning — school performance and peer relationships — rather than symptoms alone. That design let them compare which everyday behaviors most closely tracked outcomes families and schools can observe. That is an inference from the study design and the authors’ comments describing the outcomes they prioritized. (health.ucdavis.edu) ### Where can readers find the study next? The article is published in *Psychological Medicine* under the title on mediating effects of sleep quality, screen time, physical activity and Mediterranean diet on mental health and functional outcomes in early adolescence. UC Davis Health posted its summary on August 4, 2026, naming Smucny as first author and Niendam as senior author. (cambridge.org) (health.ucdavis.edu)