No solid evidence daylight savings time affects mental health, researchers find | Australia news

When the clocks “spring forward” this weekend, there may be more heart attacks and more fatal traffic accidents, but fewer crimes that involve physical harm.

Daylight saving time (DST) has been blamed for many ills, from faded curtains to confused dogs, but a major international study has found more evidence is needed for many of the claims around the time shift.

It also found only weak and inconsistent evidence that the clock change affects mental health, including rates of depression and substance abuse.

The study, which included two Swinburne University researchers – Dr Ben Bullock and Prof Greg Murray – looked at 157 studies from 36 countries over a decade.

They found while some people experienced effects similar to minor jet lag, and that some mood effects were possible, there was no association with significant declines in mental health.

The research has been published in the European Journal of Epidemiology.

“You’d think it would be quite an easy thing to study,” Bullock said.

“We know when the time’s changing, we can do almost a natural experiment. The issue is not so much being able to do those studies, it’s working out the causal mechanism.

“We can show there are correlations between daylight saving changes and changes in sleep, or accidents, but it’s very difficult to run causal studies showing it’s the actual daylight saving [to blame].”

Australia’s patchwork time zones combined with the fact that Queensland, Western Australia and the Northern Territory do not have DST have made it an oft-debated topic, particularly in the lead up to the transition.

South Australia, New South Wales, Victoria, Tasmania and the ACT residents will put their clocks forward at 2am on Sunday.

Bullock said they used epidemiological data from hospital and government records, and other sets with big sample sizes, but that their results are still correlational.

However, they did debunk the idea that changing clocks has a significant effect on mental health. There has been research showing the disruption to circadian rhythms could be linked to mood disorders.

The theory has been discussed recently in the US as they debate the future of DST. President Donald Trump is pushing to make DST permanent, and the House of Representatives has passed a bill to that effect – the Sunshine Protection Act.

Those pushing back on the idea, including the American Academy of Sleep Medicine, want it abolished in favour of permanent standard time, saying it improves mental health, with “less depression and suicide”.

In the recent study, the authors wrote that when DST begins it appears “associated with increased acute myocardial infarction and fatal traffic accidents, but also with decreased crimes involving physical harm”.

But the transition when it ends appears “associated with decreased all-cause mortality and workplace accidents, but also with increased crimes involving physical harm”.

Within the DST period, there appears to be fewer all-cause deaths and fewer traffic accidents.

“Standard time … is potentially associated with decreased sleep duration during winter,” the authors wrote, but “no clear and consistent effects on psychiatric outcomes are identified”.

Overall, they called for more robust research, and pointed out the difficulty determining causation.

While the effects of circadian rhythms have been well studied, other factors including different lengths of days in different latitudes, different health statuses, different behaviour in terms of commuting to work and social commitments and timing of medication, and even the nocebo effect – fuelled by publicity about negative health effects – could play a role.

Bullock said with so many pro and cons in the debate, and so little solid evidence, the best advice was to “make the most of the extra sunlight hours”.

“Get out there, socialise, get out with the kids and kick the footy,” he said.

It is important, he said, to avoid too much bright light late in the evening, but overall it’s a good thing to have those daylight hours.

“And at the transition times, be a bit more careful around what you’re doing, try not to plan too many big things, particularly if you do feel the effects,” he said.