Thousands of otherwise healthy people put up with a level of sleep deprivation that would drive the rest of us insane. But they are not the usual candidates for insomnia, such as shift workers or those with severe mental illness. Instead, they belong to a newly identified group of people born without the ‘comfort’ genes needed for easy sleep.
This means they are immune to the feeling of warmth and relaxation which sends an average person off to sleep within 15 minutes.
Their genes are designed instead to maintain a state of mental alertness.
This makes normal, prolonged sleep impossible so they sleep fitfully, in only short bursts.
Even then, their lack of ‘comfort’ genes may mean they struggle to get comfortable, fussing about the bedding or finding their sleeping position.
There are other so-called insomnia genes — some cause repeated periods of wakefulness in the small hours of the night or at the slightest disturbance, or drive an affected person to leap out of bed raring to start the day at 4am, but leave them exhausted by 4pm.
Until recently, insomnia was considered a purely psychological complaint triggered by stress, grief, or sleep disruption as a result of shift work or jet lag.
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http://www.dailymail.co.uk/health/article-2191145/Cant-sleep-You-inherited-insomnia-gene.html