Finding it difficult to sleep? Blame your genes, say researchers, who identified specific genetic factors that may trigger the development of sleep problems.
The findings established that insomnia was linked to the occurrence of specific variants on chromosome 7.
It also demonstrated a genetic link between insomnia and psychiatric disorders and physical conditions.
"The genetic correlation between insomnia disorder and other psychiatric disorders, such as major depression, and physical disorders such as type 2 diabetes suggests a shared genetic diathesis for these commonly co-occurring phenotypes," Murray Stein from the University of California San Diego.
"A better understanding of the molecular bases for insomnia will be critical for the development of new treatments," Stein added.
The variant on chromosome 7 is close to AUTS2 -- a gene that has been linked to alcohol consumption, as well as others that relate to brain development and sleep-related electric signalling, the researchers said.
"Several of these variants rest comfortably among locations and pathways already known to be related to sleep and circadian rhythms," Stein said.
"Such insomnia associated loci may contribute to the genetic risk underlying a range of health conditions including psychiatric disorders and metabolic disease," he said.
Twin studies in the past showed that various sleep-related traits, including insomnia, are heritable.
Based on the findings, researchers started to look into the specific gene variants involved.
In the new study, appearing in the journal Molecular Psychiatry, the team analysed DNA samples from more than 33,000 soldiers, who were of European, African and Latino descent.
Stein also compared their results with those of two recent studies that used data from the UK Biobank.
Overall, the study confirms that insomnia has a partially heritable basis.