In 2010, I reported on a study that found that insomnia sufferers are three times more likely to have a sibling or parent with insomnia, compared to healthy sleepers.
In 2011, I reported on a study that found that sleep patterns in one species of fish are genetic.
Now I've come across another two studies that appear to lend some weight to the idea that some cases of insomnia may be genetic.
A Finnish study ran from 1990 to 2009 and looked at sleeplessness symptoms in identical and non-identical twins.
The researchers found that compared to non-identical twins, identical twins were more likely to suffer from similar insomnia symptoms (difficulty falling asleep, waking during the night and feeling unrested in the morning).
New research also suggests that some insomniacs have been born without the 'comfort genes' that most of us rely on for sleep.
These so-called comfort genes are responsible for helping us feel warm and relaxed. These genes typically help us fall asleep within 15 minutes.
Those who lack these genes are instead pre-programmed to remain alert, making 'normal' sleep impossible. Instead, these individuals will often experience short bursts of fitful sleep.
It's thought that those lacking these comfort genes were intended to be the individuals who would stay awake during the night to guard primal communities.
This is still a relatively new field of research.
Insomnia is typically thought of as a purely psychological problem - however it would appear that this isn't always the case.
It's entirely possible that some people are hard wired to remain alert, making sleep naturally more difficult.
The specific genes responsible for sleep are still being researched, studied and identified. Three have thought to have been identified in mice already - one that is responsible for preventing sleep, one that is responsible for promoting sleep early in the day and promoting wakefulness in the middle of the night and one that is responsible for making it difficult to remain asleep throughout the night.
I'll be sure to keep you updated with any future findings on the genetics of sleep.
In the meantime, perhaps it's time for doctors to start asking patients about their family history when diagnosing insomnia.
Last updated: November 13, 2012