Chronic insomnia is a major public health problem. And too many people are using【C1】_____therapies, even while there are a few treatments that do work. Millions of Americans【C2】__awake at night counting sheep or have a stiff drink or【C3】__an pill, hoping it will make them sleepy.【C4】__experts agree all that self-medicating is a bad idea, and the causes of chronic insomnia remain【C5】_____.

Almost a third of adults have trouble sleeping, and about 10 percent have【C6】_____of daytime impairment that signal true insomnia. But【C7】__the complaints, scientists know surprisingly little about what causes chronic insomnia, its health consequences and how best to treat it, a panel of specialists【C8】__together by the National Institutes of Health concluded Wednesday. The panel called【C9】__a broad range of research into insomnia,【C10】__that if scientists understood its【C11】_____causes, they could develop better treatments.

Most, but not all, insomnia is thought to【C12】_____other health problems, from arthritis and depression to cardiovascular disease. The question often is whether the insomnia came first or was a result of the other diseases and how trouble sleeping in【C13】__complicates those other problems. Other diseases【C14】__, the risk of insomnia seems to increase with age and to be more【C15】__among women, especially after their 50s. Smoking, caffeine and numerous【C16】_____drugs also affect sleep.

The NIH is spending about $200 million this year on sleep-related research, some【C17】_____to specific disorders and others【C18】__the underlying scientific laws that control the nervous system of sleep. The agency was【C19】__the pane’s review before deciding what additional work should be【C20】_____at insomnia.

【C18】