Almost one-third of the population experiences symptoms of insomnia, and nearly one in five adults in the United States suffers from mental health problems. Moreover, the data shows that sleep problems continue to increase while our collective mental health steadily declines. Which begs the question, is there a cause and effect relationship between the two?

It has long been assumed that mental health problems cause trouble sleeping, but new research suggests that the reverse may also be true.

A brand new meta-analysis published in the journal of Sleep Medicine Reviews set out to look for a causal link between sleep quality and mental health. In other words, will improving the quality of our sleep also improve our mental health?

The authors compiled all of the research available on the subject, which included 65 randomized controlled trials of 72 sleep interventions on more than 8,600 participants. That’s a lot of data. But the only way to determine if sleep problems actually cause mental health difficulties is by manipulating sleep in an experimental setting and assessing whether changes in sleep lead to changes in mental health over time.

Although insomnia is most commonly associated with depression and anxiety, sleep problems have also been linked to post-traumatic stress, eating disorders, and psychosis (delusions and hallucinations). Therefore, the researchers looked for a relationship between improved sleep quality and each of these mental health issues, in addition to composite mental health.

How do you measure sleep quality?

“Good sleep” might seem like a subjective metric. However, sleep quality is typically defined by two parameters: continuity and daytime impact. Sleep continuity refers to your ability to fall asleep and stay asleep. Daytime impact denotes how refreshed you feel waking up and throughout the day.

Ultimately, sleep quality is best measured by the individual themselves, rather than an observer. You know how well you slept last night better than anyone else. Using this logic, the researchers prioritized self-reported measurements of both sleep quality and mental health. The authors note that “arguably it is the subjective experience of mental health problems that is most important.”

 Does sleep quality affect mental health?

The results showed that improving sleep quality led to significant improvements in nearly all mental health issues, though with varying degrees of impact. Improved sleep had the greatest impact on depression, anxiety, rumination, and composite mental health—yielding “a significant medium-sized effect.” Better sleep also caused a significant small-to-medium reduction in stress, and even had a small but significant effect on psychosis symptoms.

Researchers also discovered a dose response relationship, meaning that the more sleep quality improved, the more mental health improved along with it. Additionally, improving sleep was associated with better mental health no matter the severity of mental health difficulties.

With the winter months ahead and the uncertainty of the pandemic still looming, now is an excellent time to take care of your mental health. We are often reminded to prioritize mental health, but it is less often that we receive tangible action items to help us do so. Getting better sleep may be the perfect place to start.