Waking up just an hour earlier can reduce a person’s risk of developing major depression by 23%, shows a new genetic study published on May 26, 2021 in the journal. JAMA Psychiatry.
A study of 840,000 people by researchers from the University of Colorado Boulder and the Broad Institute of with And Harvard demonstrates the strongest evidence yet that chronological order – a person’s tendency to sleep over time – has an effect on depression risk.
It is also one of the first studies to determine how much or little change is needed to have any effect on mental health.
While people arose after the epidemic from work and remote school attendance – a trend that prompted many people to switch to sleep schedules later, these findings have important implications.
“We have known for a while that the relationship between sleep duration and mood is very important. But the question we often hear from doctors is: How soon do we need to change people to see benefits? ”Said Celine Vetter, senior author, CU Boulder’s assistant professor of integrative physiology. One hour was associated with a significantly reduced risk of developing depression. “
Previous observational studies have shown that night owls are twice as likely to suffer from depression when they wake up early, no matter how long they sleep. But because mood disorders can disrupt sleep patterns, researchers have a hard time deciphering what’s causing them.
Other studies have provided small samples, based on questionnaires from a single period, or did not take into account environmental factors that can influence both sleep duration and mood, which can result in confusion.
In 2018, Wetter published a long-term study of 32,000 nurses that showed that “morning risers” were 27% less likely to develop depression over four years. Is it to wake up early?
How does your genes influence when you wake up?
In order to understand more clearly whether changing the previous bedtime was a real prevention and how much it needed to be changed, lead author Iyas Daghlas turned to information from DNA The 23 and Me testing company and the UK Biobank biomedical database Daghlas then used a method called “Mendelian randomization,” which leverages the genetic correlation to help decode cause and effect.
“Our genetics are determined at birth, so some prejudices that affect other types of epidemiological research do not usually affect genetic studies,” said Daghlas, who graduated from Harvard Medical School in May.
More than 340 common genetic variants, including variables in so-called “clock genes”. PER2It is known to influence a person’s chronotype and genetics, explaining overall to 12-42% of our sleep timings.
The researchers assessed the anonymous genetic data of these variables from as many as 850,000 individuals, including data from 85,000 who wore a wearable sleep tracker for 7 days and 250,000 who responded. Sleep settings questionnaire This gives them a more detailed picture, up to an hour, of how different gene variants influence when we are asleep and awake.
In the largest group of samples, about a third of the surveyed samples identified themselves as morning cranes, 9% were night owls, and the rest in the middle. Overall, their average sleep midpoint was 3am, meaning they went to bed at 11:00 PM and woke up at 6am.
With this information, the researchers turned to another example, which included genetic information, along with anonymous medical and prescription records, and a survey on the diagnosis of major depression.
They ask, using a new statistical technique: Are people with the genetic variables that predispose them to be early risers also have a lower risk of depression?
The answer is absolutely yes.
The midpoint of sleep was one hour faster. (Half between bedtime and waking) corresponds to a 23% lower risk of major depression.
Alternatively, if people who go to bed at 1am tend to go to bed at midnight instead and sleep around the same time, they can reduce their risk by 23%, going to bed at 11 PM is about 40%.
It is not clear from studies whether early risers benefit from waking up earlier. But for those in the middle or late evening, it might be helpful to switch to the earlier bedtime period.
Bright days and dark nights
What can explain this effect?
Some research suggests that exposure to more light during the day that people who wake up in the morning tend to experience lower hormones, which can affect mood.
Others have noted that having a biological clock or a circular rhythm is a different tendency than most people can do on its own.
“We live in a society designed for the night owls, and people in the evening tend to feel as though they are in a state of inconsistent with that social clock at all times,” Daghlas said.
He stressed that large, randomized clinical trials were needed to clearly determine whether going to bed early could reduce depression symptoms, “but this study certainly changed the weight of evidence in supporting the causal effects of depression. Sleep duration against depression “
For those looking to switch to an earlier sleep schedule, Vetter offers the following tips:
“Make your days bright and your nights gloomy,” she says, “sipping your morning coffee on the balcony. Walk or bike to work if you can, and dim those electronic devices in the evening. ”
Reference Material: “Daily Setup Based on Genetic Sleep Duration and Risk of Major Depressive Disorder” by Iyas Daghlas, BS; Jacqueline M. Lane, PhD; Richa Saxena, PhD and Céline Vetter, PhD, 26 May 2021, JAMA Psychiatry.