At any given time, as many as 60 million Americans suffer from difficulties sleeping, according to the American Sleep Disorders Association, and an increasing number of them reach for sleeping pills to help make it through the night. They spent 14 million prescriptions in 1992, the Sleep Disorders Association reports. And according to Nielsen Marketing Research Data, the use of nonprescription sleeping pills far outstrips prescription medications. The most recent sales figures show that over-the-counter sleeping pills ran an estimated $73 million annually in 1993 -- nearly a 15 percent increase from 1987.

The long-term risks of prescription sleeping pills -- including barbiturates, which depress activity in the brain; benzodiazepines, which help relieve anxiety; and antihistamines, which block chemicals released during an allergy attack and have a sedative effect -- are well documented. Among the side effects are poor quality sleep, drowsiness that continues into the next day and psychological dependence. When the drugs are discontinued, they also can create so-called "rebound" insomnia, a physiological reaction that lasts a couple of days and is more apt to occur with high doses of sleeping pills.

The team examined a dozen unpublished studies submitted to the Food and Drug Administration by drug companies for approval of nonprescription sleeping pills. They found that eight of the studies involved hospitalized patients. Since most users of nonprescription sleeping pills live at home and suffer from mild insomnia, some experts question whether these findings apply. In addition, half the studies tested the medications for only one night, and the longest study was conducted for 14 days, although use tends to be for much longer.