It’s that time of year again. On November 6th, most of the United States will participate in that semi-annual ritual of changing the clocks by an hour. In the fall we gain an hour of sleep time, or an hour of loafing around on a Sunday morning…how bad could it be?
Our circadian clock is an elaborate system of chemical signals and hormones reacting to all sorts of environmental inputs such as light, feeding, and even temperature. The system is quite elegant, with many interconnected parts that when working well keeps us healthy with brains and metabolism in tip top condition. We can compare the circadian system to an orchestra playing a symphony…if everyone is playing the same piece, well-timed and in tune, it sounds wonderful, but if one horn is off pitch, the whole experience can be ruined.
Sleep is necessary for the brain to wash away the build-up of toxic byproducts of cell metabolism accumulated over the day. Without sleep, we very quickly lose the ability to function. The effects of acute total sleep deprivation are very obvious. In folks with bipolar disorder it can cause a manic episode and seizures in those with epilepsy.
Long term, even low level sleep deprivation can contribute to a myriad of bad health effects, such as obesity, depression, and dementia. It also increases risks of heart attacks and motor vehicle accidents. While one hour difference a couple times a year seems small, evidence shows us that the delicate human circadian clock doesn’t adjust well to the abrupt difference in time.
When looking at the acute affects of the one hour transition of daylight savings, there are a host of papers showing negative effects on workplace injuries, productivity, traffic accidents, and heart attacks. But what about mental health? Older papers remark on no changes in suicidal behaviors or increase in inpatient or outpatient admissions during DST changes, but large Scandinavian registries over decades give us the ability to get a bigger picture of daylight savings in spring and fall and mental health.
Overall admissions could balance out if each transition (forward or backward) has different effects on major depressive disorder or mood disorders with more seasonal components.
It seems that the single hour change is not disruptive enough to lead to an increase hospitalization for bipolar manic episodes in this Finnish study (whereas there are cases of mania caused by bigger time shifts due to air travel). However, less dramatic but negative behavioral effects are seen in children during the days following daylight savings switches.