五、失眠

　　Chronic insomnia is a major public health problem. And too many people are using__1__ therapies，even while there are a few treatments that do work. Millions of Americans __2__awake at night counting sheep or have a stiff drink or __3__an pill，hoping it will make them sleepy.__4__ experts agree all that self-medicating is a bad idea，and the causes of chronic insomnia remain__5__.

　　Almost a third of adults have trouble sleeping，and about 10 percent have__6__ of daytime impairment that signal true insomnia. But __7__the complaints，scientists know surprisingly little about what causes chronic insomnia，its health consequences and how best to treat it，a panel of specialists __8__together by the National Institutes of Health concluded Wednesday. The panel called__9__a broad range of research into insomnia，__10__that if scientists understood its __11__causes，they could develop better treatments.

　　Most，but not all，insomnia is thought to __12__other