What does it mean to say someone has insomnia? Most of us see this as a dead simple question - insomnia means you struggle to get to sleep or stay asleep and end up getting way less sleep than you need.

But when scientists examined an enormous amount of accumulated data on self reports of insomnia and people's actual sleeping patterns recently, that's not what they found. It turns out this question isn't a head slapper after all. In fact, it's a gateway into complicated sleep science that suggests our expectations and belief play a far bigger role in determining how rested we feel than most of us ever suspect.

Insomnia often isn't about how much you sleep.

The research by University of Alabama psychologist Kenneth Lichstein examined data from 20 previous sleep studies to see how closely correlated bad sleep is with complaints of insomnia. The short answer is that these two things overlap surprisingly little. Tons of people who have objectively bad sleep as measured by surveys, brain waves, and sleep diaries actually don't feel troubled about their sleep at all. They don't think of themselves as insomniacs in the least.

On the other hand, the opposite is also true. Lichstein uncovered a huge group of people who complained bitterly of insomnia, but yet, when measured by sleep researchers, seemed to sleep pretty well.

"Lichtstein reports that 37 per cent of individuals complaining of insomnia 'do not have poor sleep by conventional standards'. This is not to say that their sleep was flawless, or that it wasn't worse than average in some way, but it certainly falls in the normal range. On the other hand, many individuals with non-normal levels of sleep problems are able to exist as if free from insomnia," says the British Psychological Society Research Digest blog summing up the findings.

Exhaustion is a state of mind.  

While this science is startling, it's hardly the first evidence to come out that how you feel about your sleep might not be all that closely related to how many hours you actually spend asleep. For instance, recent research on the sleep habits of hunter gatherer bands living much like our long-ago ancestors did found modern humans actually don't get much less sleep than our tribal forebears. The problem with our sleep these days might mostly be our expectations, the scientists concluded.

Another study on the 'placebo' effect and sleep found essentially that you can fake your way out of exhaustion after a bad night's sleep by simply telling yourself you feel OK. While no one suggests this is a long-term solution to sleep complaints, the results add more evidence to the case that insomnia and exhaustion are more about attitude than most of us understand.

Can you think your way to feeling more rested?

What's the bottom line of all this research? In short, that lots of folks effectively psyche themselves out of feeling more well rested by worrying excessively about 20 minutes of tossing and turning before sleeping, or a perfectly normal level of nighttime wakefulness. Stressing about sleep in this way obviously makes it harder to go to sleep peacefully, creating a self-fulfilling prophesy of so-called insomnia.

While there are certainly many people with serious sleep problems whose account of their suffering shouldn't be doubted and who need medical solutions, science suggests that there are also plenty of folks with milder sleep issues who would benefit from simply chilling out and lowering their expectations. (Lichtstein recommends cognitive behavioral therapy, questioning your expectations about sleep, and meditation in cases where that's way easier said than done.)