Insomnia is probably the most common health complaint. Even after treatment, poor sleep remains a persistent vulnerability for many people.

Researchers have found, for the first time, seven risk genes for insomnia. With this finding in the journal Nature Genetics, the researchers have taken an important step towards the unravelling of the biological mechanisms that cause insomnia. In addition, the finding proves that insomnia is not, as is often claimed, a purely psychological condition.

In a sample of 113,006 individuals, the researchers found 7 genes for insomnia. These genes play a role in the regulation of transcription, the process where DNA is read in order to make an RNA copy of it, and exocytosis, the release of molecules by cells in order to communicate with their environment.

One of the identified genes, MEIS1, has previously been related to two other sleep disorders: Periodic Limb Movements of Sleep (PLMS) and Restless Legs Syndrome (RLS). The researchers could conclude that the genetic variants in the gene seem to contribute to all three disorders. Strikingly, PLMS and RLS are characterized by restless movement and sensation, respectively, whereas insomnia is characterized mainly by a restless stream of consciousness.

The researchers also found a strong genetic overlap with other traits, such as anxiety disorders, depression and neuroticism, and low subjective wellbeing. "This is an interesting finding, because these characteristics tend to go hand in hand with insomnia. We now know that this is partly due to the shared genetic basis", says first author of the study.

The researchers also studied whether the same genetic variants were important for men and women. "Part of the genetic variants turned out to be different. This suggests that, for some part, different biological mechanisms may lead to insomnia in men and women", says research lead. "We also found a difference between men and women in terms of prevalence: in the sample we studied, including mainly people older than fifty years, 33% of the women reported to suffer from insomnia. For men this was 24%."

The risk genes could be tracked down in cohorts with the DNA and diagnoses of many thousands of people. The UK Biobank - a large cohort from England that has DNA available - did not have information as such about the diagnosis of insomnia, but they had asked their participants whether they found it difficult to fall asleep or to have an uninterrupted sleep. By making good use of information from slaapregister.nl (the Dutch Sleep Registry), the UK Biobank was able, for the first time, to determine which of them met the insomnia profile. Linking the knowledge from these two cohorts is what made the difference.

https://www.nature.com/ng/journal/vaop/ncurrent/full/ng.3888.html