One-third of the 32 patients in the study have relatives with excessive sleepiness to varying degrees.

WSJ: Unraveling the Riddle of Too Much Sleep

Right now, it is only approved for use in narcoleptics suffering from excessive sleepiness during the day.

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Its lead drug, modafinal, is a widely used treatment for excessive sleepiness that is also awaiting approval for treating ADHD in children.

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"There are 40 million people in America alone who have excessive sleepiness as their major symptom, and that's who we're after, " he says.

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But it quickly became more than a narcolepsy medication, as doctors used it to treat side effects from other medicines and other types of excessive sleepiness.

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Now, the drug is also approved for excessive sleepiness.

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Instead, it was an effective treatment for narcolepsy, a disorder marked by excessive daytime sleepiness.

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Of course, the vast majority of people with excessive daytime sleepiness don't have hypersomnia most just don't get enough sleep at night.

WSJ: Unraveling the Riddle of Too Much Sleep

Take, for instance, ProVigil, which is used to treat excessive daytime sleepiness.

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After all, if Xyrem got knocked by 20 out of 22 advisers to the Food and Drug Administration as a treatment for pain, how could it be something regulators could OK just to ease some excessive daytime sleepiness?

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And when sleeping pills aren't enough to help patients stay alert, a wakefulness drug called Provigil is already approved for excessive daytime sleepiness caused by narcolepsy, sleep apnea and shift-work sleep disorder--the exhaustion brought on in some people by working the night shift.

FORBES: Sleep On Demand