The short-term effects of daylight saving time clock changes on mental and physical health in England has been examined in a large population-based study using routinely collected NHS data.

The study aimed to assess whether the spring and autumn clock changes are associated with acute changes in healthcare presentations for selected mental and physical health conditions.

Published in the BMJ, the research was led by the Medical Research Council (MRC) Integrative Epidemiology Unit at the University of Bristol, alongside colleagues from the University of Bristol, University of Oxford, University College London and the Norwegian University of Science and Technology in Trondheim, Norway.

Some previous studies have suggested that daylight savings clock changes, particularly the spring clock change, have a detrimental effect on health, leading to calls for them to be abolished.

The researchers conducted a retrospective cohort analysis using linked primary care, hospital admission and emergency department records from the Clinical Practice Research Datalink GOLD database.

Impact of daylight saving time clock changes

The cohort included 683,809 individuals who experienced at least one relevant health event in the eight weeks surrounding the spring or autumn daylight saving clock changes between 2008 and 2019.

Outcomes examined included major acute cardiovascular disease, anxiety, depression, sleep disorders, eating disorders, self-harm, road traffic injuries and psychiatric conditions presenting to emergency departments.

Age eligibility varied by condition, with cardiovascular events restricted to those aged 40 years and over, and most other outcomes assessed from aged 10 upwards.

The main findings showed that the week following the autumn clock change was associated with modest but statistically significant reductions in several health events. Specifically, anxiety disorders decreased by 3% (from 17.3 to 16.7 events per day, 95% CI 0.95–0.98), major acute cardiovascular disease by 2% (from 50.0 to 48.9, 95% CI 0.96–0.999), depression by 4% (from 44.6 to 42.7, 95% CI 0.95–0.97), psychiatric presentations to accident and emergency by 6% (from 3.5 to 3.3, 95% CI 0.90–0.98), and sleep disorders by 8% (from 5.4 to 4.9, 95% CI 0.87–0.97).

Reductions in sleep disorder diagnoses persisted for up to four weeks, although the effect weakened over time. In contrast, there was little evidence that the spring clock change was associated with changes in overall event rates across the outcomes studied.

The researchers concluded that increased morning light exposure and additional sleep following the autumn clock change may underpin the observed benefits regarding reductions in mental and physical health events and demand for NHS services. This morning sunlight exposure can help to resent the body clock and improve sleep, as well as having the potential to lower cardiovascular disease risk by reducing blood pressure, they added.

‘A more complete picture’

Several limitations were noted, including reliance on recorded healthcare contacts rather than symptom onset, potential misclassification in electronic health records and limited ability to capture subclinical effects or delayed presentations. Seasonal confounding and variation in school holidays could not be fully accounted for, the researchers added.

And while no firm conclusions can be drawn about cause and effect due to the observational nature of the study, they said the results provide a more complete picture of the effect of the clock changes on demand for health services than previous studies as a result of the 12 years of broadly representative NHS data.

Corresponding author Melanie de Lange, a Wellcome-funded epidemiology PhD student at Bristol Medical School’s Population Health Sciences and MRC Integrative Epidemiology Unit, said: ‘Our study contributes to the ongoing debate about England’s clock change policy. Future research should explore the mechanisms underlying the reduction in health events that we observed after the autumn clock change.’

The researchers also called for further research into the impact of daylight saving time clock changes in children and adolescents and long-term health impacts in countries that have abolished clock changes. This will better inform future policy decisions, they added.

Reference
de Lange M et al. Acute effects of daylight saving time clock changes on mental and physical health in England: population based retrospective cohort study. BMJ 2025 Dec 17;391:e085962.