Lower levels of physiological regulation could make some depressed individuals more vulnerable to the negative impacts of sleep disturbances, according to new research Journal of Psychiatric Research.

The researchers were particularly interested in how the naturally occurring variation in heart rate during the breathing cycle, known as respiratory sinus arrhythmia, was related to sleep and depression.

“Depression is one of the most common mental health problems in the world, and people who have had a depressive episode are 50% more likely to suffer from future depression. People who have sleep problems, such as short sleep or difficulty falling or staying asleep, are at increased risk for depression,” said study author Jessica L. Hamilton, a postdoctoral scholar at the University of Pittsburgh Department of Psychiatry.

“We were interested in understanding whether poor sleep would predict who experienced higher levels of depression symptoms over a 2-week period, and whether we could identify a biological factor that indicated which people were most impacted by poor sleep. We chose to focus on sleep and physiological regulation because these are factors that are be changeable and can be targeted in treatment.”

For the study, 102 participants completed the Trier Social Stress Task — an experimentally verified stress-inducing scenario — while the researchers monitored their heart rate variability. All of the participants were young adults with prior depression.

The participants were given a few minutes to prepare a 3-minute speech about themselves, which they then delivered in front of a neutral experimenter and camera. They were then asked to solve an impromptu math problem.

After this laboratory assessment of physiological reactivity, the participants completed daily surveys regarding their sleep duration, insomnia symptoms, and depressive symptoms for two weeks.

The researchers found that shorter sleep durations and fluctuations in insomnia symptoms both predicted higher depressive symptoms. They also found that impairments in sleep were the most detrimental for those with lower resting respiratory sinus arrhythmia.

“Our study suggests that it is important to pay attention to sleep — particularly for those who have had depression in the past. Regularly not getting enough sleep and having individual nights of bad sleep may contribute to higher depression symptoms, which may increase the risk of who will go on to develop future depression,” Hamilton explained to PsyPost.

“Although poor sleep is not good for anyone, our work also suggests that people who have lower levels of physiological regulation are most impacted by poor sleep and at risk for depression symptoms following nights of poor sleep. This is likely because poor sleep impairs how well a person can regulate emotions and stress on a day-to-day basis — and someone who already has difficulty with this (as indicated by their physiology) may be doubly at risk.”

The study — like all research — includes some limitations.

“Although depression symptoms may indicate risk for future depression, it will be important to examine whether these risk factors actually predict who goes on to have another depression episode,” Hamilton said.

“Our measures of sleep were also self-reported on a day-to-day basis, so it will be important to conduct this work with behavioral sleep trackers. With an increasing market of wearables, we will be advance this work by monitoring a person’s sleep and physiological regulation in the real world.”

“In the future, this will be important to identify who is at risk for depression and when, such as when they have poor sleep, and intervene when people need it most. We hope this work inspires others to investigate which individuals are most affected by poor sleep, and whether altering a person’s sleep or physiology can prevent the onset of depression,” Hamilton said.

But the research adds to a growing body of evidence that links bad sleep to depression.

“Sleep is really important to your physical and mental health. Not getting enough sleep or having sleep problems are often accepted as ‘typical’ or part of life, especially among young adults. However, getting a healthy amount and quality of sleep are really important for your mood and emotional well-being,” Hamilton told PsyPost.

“Although our study did not address the causes of poor sleep, other research suggests that it is important to have a wind-down routine every night to relax and for people to stop using electronic devices in bed or within the 30 minutes before trying to go to sleep. It’s also important to wake up at the same time every day, which can help improve your quality and quantity of sleep and your mood.”

The study, “Sleep disturbance and physiological regulation among young adults with prior depression“, was authored by Jessica L. Hamilton, Jonathan P. Stange, Taylor A. Burke, Peter L. Franzen, and Lauren B. Alloy.