Sleeping Less Than Eight Hours Linked to Depression and Anxiety in New Study

Sleeping is important for mental health. Lauren DeCicca/Getty Images

Lack of sleep may cause more than just dark circles under your eyes. New research found that people who sleep less than the reccomended eight hours are also more likely to have repetitive negative thoughts, a finding that could explain the link between sleep and mental health.

Sleep-deprived individuals are less able to quickly shift their attention away from distressing stimuli. As a result, negative thoughts may stick with them throughout the day more strongly than better rested people. The findings, published in Journal of Behavior Therapy and Experimental Psychiatry, suggest that lack of sleep really can make us sad. The study also points toward rest as a key treatment options for certain mental health conditions, such as depression and anxiety.

Related: How To Sleep Well? Fill Your Life With Purpose, Study Says

For the study, researchers assessed the sleep habits of 52 volunteers who also had moderate to high levels of repetitive thoughts, indicated by their score on a psychological test known as the Perseverative Thinking Questionnaire. The volunteers looked at photos and images designed to trigger a negative emotional response, such as guns or knives, and also neutral and positive images. They studied the volunteers' eye movement, paying particular attention to how quickly they averted their eyes from the disturbing images.

Related: Sleep Deprivation Disrupts Brain Activity As Much As Alcohol

According to the results, individuals who were sleep deprived—defined by sleeping less than eight hours a night—were slower to look away from the disturbing images. The study concluded that this problem may go even deeper, suggesting that sleep-deprived individuals may also have problems diverting their attention away from negative thoughts and ideas. The researchers hypothesized that such thoughts may put these individuals at greater risk for certain mention health conditions, such as depression and anxiety.

"This repetitive negative thinking is relevant to several different disorders like anxiety, depression and many other things," said Meredith Coles, a psychology professor at Binghamton University and study co-author said in a statement. This work is novel, Coles says, "in that we're exploring the overlap between sleep disruptions and the way they affect these basic processes that help in ignoring those obsessive negative thoughts."

The potential link between depression and sleep deprivation is not entirely unrecognized. According to the National Sleep Foundation, people with insomnia are 10 times more likely to develop depression than people who sleep well. But scientists see the relationship between sleep and mental health as one that is too complex for a simple conclusion like not sleeping makes you sad.

If lack of sleep does contribute to depression and anxiety, then addressing sleep problems could also be key to alleviating these conditions as well.