New research published in Human Brain Mapping provides evidence of a shared neural mechanism that underlies sleep disturbance and mental disorders in preadolescents. The findings indicate that sleep disturbance and mental health problems are both related to the connectivity between and within two important brain networks.
“I noticed the importance of sleep years ago when I read several papers about the immediate amyloid protein deposition in the brain after short-term sleep deprivation. Amyloid is neurotoxic waste in the brain and needs to be transported out by cerebrospinal fluid,” said study author Ze Wang, an associate professor of diagnostic radiology and nuclear medicine at the University of Maryland School of Medicine.
“But cerebrospinal fluid is basically static most of the time. The best time to have more cerebrospinal fluid and increased flow rate is at night when you lay down and fall asleep. It is this time that our cerebral blood flow reduces. Because our brain has a fixed size, the reduction of cerebral blood flow creates space for cerebrospinal fluid and the inhomogeneous change of blood flow creates power for cerebrospinal fluid to flow and then transport the neural waste out. This is why our brain generates two times as much cerebrospinal fluid at night than daytime.”
“With this in mind, I have been looking for opportunity to investigate the effects of sleep on the brain,” Wang explained. “The opportunity came when I got access to Adolescent Brain Cognitive Development data, which contains brain images and neuropsychological measures, biological measures, and many other measures for the public research community to use.”
The Adolescent Brain Cognitive Development research project is a 10-year-long longitudinal study that launched in 2016 and has enrolled nearly 12,000 youth aged 9 to 10 at 21 research sites around the United States. “The data is so big that it took me and my lab members two months to download them and took me another month to learn what information they provided,” Wang noted.
Wang said one of his postdoctoral researchers, Nils Yang, came up with the idea of investigating the links between functional brain connectivity, sleep disturbances, and mental health problems. For their study, the team of researchers analyzed a dataset 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 measures on year later.
The study found that “a lack of sleep in teens is associated with altered connections between and within two important brain networks: one is the dorsal attention network, which is mainly responsible for attention, memory, and inhibition control; the other is the default mode network, which has been shown to have an important role for facilitating general brain function,” Wang explained.
Greater sleep deficits were associated with greater mental health problems, as measured via 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 subsequent increases in mental health problems one year later and greater mental health problems also predicted subsequent increases in sleep disturbance.
Importantly, Wang and his team found that the relationship between sleep disturbance and mental health problems was mediated by the brain connections within and between the dorsal attention network and the default mode network. The dorsal attention network and default mode network are typically anticorrelated, meaning that when one is active, the other is usually inactive. But sleep disturbances and mental health problems were associated with strengthened 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 disturbance a year later.
“Nowadays, teenagers are getting less and less sleep because of all kinds of excitations,” Wang said. “Unfortunately, this comes with consequences. One possible consequence is the harm to mental health, which may reciprocally impact sleep quality and start a worse-to-worse cycle. Another possible consequence is the change of brain connections. These consequences may last for a long time. Because the adolescent brain is still under rapid development, sustained sleep deficits may lead to permanent impairment to the brain and to the cognitive functions.”
“Getting good sleep back is crucial to teens’ brain and mental health. In extreme cases where sleep quality is difficult to improve, an alternative potential approach can be some intervention that can specifically improve brain function connectivity.”
The study, “Functional connectome mediates the association between sleep disturbance and mental health in preadolescence: A longitudinal mediation study“, was authored by Fan Nils Yang, Tina Tong Liu, and Ze Wang.