A LARGE population-based study has found that the autumn daylight saving time (DST) clock change in England is associated with a short-term reduction in several mental and physical health events, while little evidence was found of adverse or beneficial effects following the spring clock change.
Researchers analysed electronic health records from 683,809 individuals registered with English general practices contributing to the Clinical Practice Research Datalink GOLD database. These data were linked to hospital admissions and accident and emergency records, covering the period from 2008 to 2019. The study examined health events occurring in the eight weeks surrounding the spring and autumn clock changes.
The outcomes of interest included diagnoses of anxiety, depression, sleep disorders, eating disorders, major acute cardiovascular disease, road traffic injuries, and self-harm, recorded in either primary or secondary care. Psychiatric conditions presenting to accident and emergency departments were also included. Event rates in the week following each clock change were compared with a control period consisting of the four weeks before the change and weeks two to four afterwards.
What The Clock Change Means for Mental and Physical Health
Following the autumn clock change, five outcomes showed modest but statistically significant reductions in daily event rates. These included anxiety, depression, sleep disorders, acute cardiovascular disease, and psychiatric conditions presenting to emergency care. For example, rates of depression fell from 44.6 to 42.7 events per day per year per region, while sleep disorder diagnoses decreased from 5.4 to 4.9 events. No clear reductions were observed for eating disorders, road traffic injuries, or self-harm.
Clock Change Effects Vary by Season, Study Suggests
In contrast, the spring clock change, often hypothesised to have negative health effects due to sleep disruption, was not associated with meaningful changes in any of the health outcomes studied.
The authors suggest that increased morning light exposure following the autumn clock change may contribute to the observed reductions, particularly for mental health and sleep-related conditions. However, they caution that electronic health records capture the date of clinical recording rather than the precise onset of symptoms, which may limit interpretation of acute effects.
Overall, the findings challenge assumptions that daylight saving time transitions are uniformly harmful and highlight the need for further research into how seasonal light changes influence population health.
Reference
De Lange M A et al. Acute effects of daylight saving time clock changes on mental and physical health in England: population based retrospective cohort study.BMJ.2025; 391:e085962
