Neuroscience research suggests a shared mechanism underlies both sleep disturbance and mental disorders

New research published in Mapping of the human brain provides evidence for a shared neural mechanism underlying sleep disturbance and mental disorders in preadolescents. The findings indicate that sleep disturbance and mental health problems are related to connectivity between and within two important brain networks.

“I realized the importance of sleep years ago when I read several articles about the immediate deposition of amyloid protein in the brain after short-term sleep deprivation. Amyloid is neurotoxic debris in the brain and needs to be transported by the cerebrospinal fluid,” said the study’s author. Ze Wangassociate professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine.

“But the cerebrospinal fluid is basically static most of the time. The best time to have more spinal fluid and a higher flow rate is at night when you lie down and fall asleep. It is at this time that our cerebral blood flow is reduced. Because our brain is a fixed size, the reduction in cerebral blood flow creates space for the cerebrospinal fluid, and the inhomogeneous change in blood flow creates energy for the cerebrospinal fluid to flow and then transport neural debris. This is why our brain generates twice as much cerebrospinal fluid at night than during the day.”

“With this in mind, I have been looking for opportunities to investigate the effects of sleep on the brain,” explained Wang. “The opportunity came when I had access to the Adolescent Brain Cognitive Development data, which contains brain imaging and neuropsychological measures, biological and many other measures for use by the public research community.

The Cognitive Development of the Adolescent Brain research project is a 10-year longitudinal study that launched in 2016 and has enrolled nearly 12,000 9- to 10-year-olds at 21 research sites in the United States. “The data is so big that it took me and my lab members two months to download it and it took me another month to learn what information they provided,” Wang said.

Wang said that one of his postdoctoral researchers, Nils Yang, came up with the idea to investigate the links between functional brain connectivity, sleep disorders, and mental health problems. For his study, the team of researchers analyzed a data set that included 9,350 children who had undergone functional magnetic resonance imaging (fMRI) and completed behavioral assessments. Of this sample, 8,845 children completed follow-up measurements one year later.

The study found that “lack of sleep in adolescents is associated with altered connections between and within two important brain networks: one is the dorsal attention network, which is primarily responsible for attention control, memory, and inhibition; the other is the default mode network, which has been shown to play an important role in facilitating overall brain function,” Wang explained.

Greater sleep deficits were associated with greater mental health problems, as measured through the Child Behavior Checklist, a widely used diagnostic questionnaire. The relationship between sleep deficits and mental health problems was bidirectional. In other words, greater sleep deficits predicted later increases in mental health problems a year later, and greater mental health problems also predicted later increases in sleep disorders.

Importantly, Wang and his team found that the relationship between sleep disturbance and mental health problems was mediated by brain connections within and between the dorsal attention network and the default mode network. The dorsal attention network and the default mode network are usually anti-correlated, meaning that when one is active, the other is usually inactive. But sleep disturbances and mental health problems were associated with stronger connectivity between the two networks.

Children who had less segregation between the dorsal attention network and the default mode network at the start of the study tended to have worse mental health problems and worse sleep disturbances a year later.

“Today, teenagers are getting less and less sleep due to all kinds of excitements,” said Wang. “Unfortunately, this comes with consequences. One possible consequence is damage to mental health, which can reciprocally affect sleep quality and start a cycle from worse to worse. Another possible consequence is the change of brain connections. These consequences can last a long time. Because the adolescent brain is still developing rapidly, sustained sleep deficits can lead to permanent decline in brain and cognitive function.”

“Regaining good sleep is crucial for adolescent brain and mental health. In extreme cases where sleep quality is difficult to improve, an alternative potential approach may be some intervention that can specifically improve the connectivity of brain function.”

The study, “The functional connectome mediates the association between sleep disturbance and mental health in preadolescence: a longitudinal mediation study.“, was written by Fan Nils Yang, Tina Tong Liu and Ze Wang.