The brain cells that cause insomnia have been identified for the first time by scientists.
In a “breakthrough” study, scientists have identified for the first time brain cells linked with insomnia – and found strong genetic links with depression and anxiety.
The discovery is a major step towards understanding what causes a terrible night’s sleep – which is more likely to be linked with mental health than sleeping traits.
Insomnia is one of the world’s most common disorders, with 770 million people suffering from chronic insomnia worldwide.
One in ten people experience poor sleep, with severe consequences the next day.
But scientists at two Dutch universities assembled a large group to better understand what causes the disorder.
Prof Guus Smit, a neurobiologist at VU-University, Netherlands, said: “These findings are a breakthrough, since we can now for the first time start searching for underlying mechanisms in individual brain cells in the laboratory.”
The researchers are already shifting their focus to study areas of the brain responsible for emotion to better understand why some of us struggle to nod off.
Professor Eus Van Someren, from the Netherlands Institute for Neuroscience, who also participated in the study, said: “Our first results in that direction are already spectacular.
“A very important finding, because we have always searched for causes of insomnia in the brain circuits that regulate sleep.
“We have to shift our attention to the circuits that regulate emotion, stress and tension.”
Professors at the universities worked with a large group of scientists and cohorts, including the UKBiobank and US-based company 23andMe, to find out where in the brain insomnia risk genes exert their effect.
They were the first to assemble DNA and sleep data from 1.3 million people – the largest genetic dataset ever.
Lead study author and doctoral student Philip Jansen said: “It is fascinating that we can nowadays start to understand what happens at the micro-level of molecules and cells in the brain, just because we can assemble so many data at the macro-level, worldwide”.
The team identified the cell types, areas and biological processes in the brain that mediate the genetic risk of insomnia, bringing them closer towards understanding the biological mechanisms behind the disorder.
Vladimir Vacic, a senior scientist at 23andMe, said: “This study is an immense step forward in understanding the genetic background of insomnia.
“The findings underline that insomnia is a serious condition, because of the shared genetic risk of psychiatric disorders metabolic disturbances involved in obesity and diabetes.”
While existing treatment alleviates symptoms, most sufferers feel that they are still at risk of struggling to sleep at night.
Vulnerability to insomnia runs in families and seems hard-wired in the brain and only a few genes that cause this had been identified.
Other challenges included trying to determine where in the brain ‘insomnia risk genes’ exerted their disturbing role – which is crucial to developing better treatments.
In this new study, researchers identified more than 950 (956) genes in which variants contributed to the risk of insomnia and investigated which biological processes, cell types and brain areas utilise these genes.
They found that part of these genes had an important role in the functionality of axons – parts of the brain cells that allow them to communicate with each other.
Another significant part of the insomnia risk genes was active in specific cell types of parts of the frontal cortex and the subcortical nuclei of the brain.
These areas had also recently been marked as ‘suspect’ in brain imaging studies of people suffering from insomnia, meaning their findings were consistent.
Prof Danielle Posthuma, from VU Amsterdam, said: “Our study shows that insomnia, like so many other neuropsychiatric disorders, is influenced by hundreds of genes, each of small effect.
“These genes by themselves are not that interesting to look at – what counts is their combined effect on the risk of insomnia.
“We investigated that with a new method, which enabled us to identify specific types of brain cells, like the so-called medium spiny neurons.”
The study was published in Nature Genetics journal.
By Laura Sharman & Joe Mellor