dreaming sleeping Andrew Kelly/Reuters

Americans as a whole are really bad at sleeping.

In a survey of more than 70,000 people in the US about a third of respondents said that they snoozed for less than seven hours per night. About 38% said that they'd fallen asleep during the day at least once in the month prior.

It's no suprise, then, that millions of Americans suffer from a wide range of sleep disorders. But their actual diagnoses may not be so straightforward.

Many people who have trouble falling asleep and staying asleep assume that they have insomnia, but they shouldn't be so quick to jump to that conclusion, Patrick Fuller, associate professor of neurology at Harvard Medical School told Tech Insider.

"People throw that word around, but most cases of insomnia are not primary insomnia," Fuller said. "In other words, that's not the main issue."

If you actually go to a sleep clinic and do the whole rigmarole of getting hooked up to electrodes and monitors and spending a (somewhat uncomfortable) night in the clinic, you'll probably find that you don't actually have insomnia.

Of the people that come in with a primary complaint of insomnia, Fuller said, only 15% or so are truly insomniac for a brain reason. "They just biologically can't sleep."

So what's wrong with everyone else? Most people often have other neuropsychiatric issues driving the insomnia, such as depression and, more commonly, anxiety.

"If you take care of the anxiety, guess what happens," Fuller said. "You take care of the insomnia."

Still, if you think you might actually have insomnia, the best thing to do is to make an appointment with a sleep doctor. According to the National Institutes of Health, people with insomnia often lie awake for long periods before falling asleep, sleep for only short bursts of time, lie awake for much of the night, wake up feeling as if they hadn't slept at all, or wake up way earlier than they need to.

If that sounds like you, you should probably get checked out.

But in the mean time, make sure you're doing everything possible to set the stage for a good night's sleep before you even shut your eyes. Dim your lights and stay away from smart phone and iPad screens within two hours of bedtime. Wake up at the same time every day. Exercise. Limit alcohol intake. And skip those late afternoon coffees.

Sweet dreams!