Nanogirl Dr Michelle Dickinson: Is daylight savings bad for your health?

It may be better for your health to forgo the lie-in tomorrow and get as much sunlight as you can. Photo / 123RF

Tomorrow marks the end of daylight saving time, and at 2am clocks all over New Zealand will jump back one hour. With the added benefit of it also being Easter Sunday, that means many of us will enjoy a delightful and restful extra hour of sleep.

Although it may seem like a good thing at the time, the additional snooze time tomorrow may actually not be as good for us long term as it might feel.

Research published in the journal Epidemiology looked at patient data over seven years from 185,419 depression diagnoses recorded under the Danish psychiatric central research register. They found a significant spike in the number of patients diagnosed with depression right after the clocks went back for daylight saving time. The 11 per cent increase in diagnosis lasted for about 10 weeks after the time change before returning back to normal.

Initially, it was thought that the change in sleep patterns could be the cause, in a similar way to how jet lag can affect mood and concentration. This theory was thrown out, however, when the researchers found no change in depression diagnosis during the other half of the year when the clocks went forward by an hour.

Instead, scientists think that the increased depression is most likely caused by a change in the exposure to daylight.

How can losing just an hour of light at the end of the day change how we feel?

Our circadian rhythm or internal body clock is an elaborate system of chemical signals and hormones, which react to different environmental inputs including light, food and temperature.

When everything is in balance, our brains and metabolism are healthy. If something gets out of sync though, then an alteration in our brain chemicals can potentially lead to depression, mood swings and feelings of sadness.

Sunlight is one of the major factors controlling our circadian rhythm, and the change in sunlight exposure is thought to be connected to the increase in depression rates, rather than the change in sleep pattern.

For most of us, we probably won't see much of the extra hour of morning light we get tomorrow. Instead many of us will appreciate a lie-in and sleep through the sunshine, grabbing an extra hour of sleep. We'll also experience one less hour of daylight in our evening. This additional darkness in our day is potentially significant in affecting our mental health.

In addition to the lack of daylight, the act of moving our clocks back may also cause us to have a mental shift as we dread the thought that the cold, wet weather of winter is coming. These negative thoughts can also prompt the symptoms of depression.

The debate over the effects of daylight saving time has been going on since 1895 when George Hudson first suggested to the Wellington Philosophical Society that they consider moving time around twice a year to accommodate the longer hours of summer.

Evidence now shows that the negative associations with daylight saving time transitions include disturbed sleep, cardiovascular function and possibly an increased tendency for fatal traffic accidents and serious workplace injuries!

So how should we maximise the additional hour tomorrow while still taking care of our mental health? The best solution is to get maximum exposure to natural light through the day.

This may mean shifting your schedule to wake up earlier so that you get as much sunlight as you can, and then using that time to be outside such as for an early morning walk.

Basically, the best solution is forgoing the lie in and getting up early anyway.