It started with just a couple of sleepless nights. So you cut the caffeine, turned down the lights, and turned off the TV. You abandoned your Blackberry and turned to warm, soothing baths. But nothing has helped—you're still tossing and turning. Your body is desperate for sleep.

What's going on? It could be stress. "Thanks to the economy, there's been a big increase in stress, especially in women," says Alan Lankford, Ph.D., president of the Sleep Disorders Center of Georgia. "And stress can have a big impact on falling and staying asleep." But if you've tried all the usual sleep advice and consulted your doctor to rule out underlying issues—and you're still lying awake at night—consider easing yourself into sleep with melatonin, your body's natural sleep aid.

The Science of Sleep

Ever wonder why you start feeling drowsy when nighttime rolls around? Or why people seem to have natural cycles of sleep and wakefulness? It's because of a hormone called melatonin that regulates your daily rhythm. Acting as the body's sandman, melatonin slows body functions and lowers blood pressure; this causes a dip in core body temperature and helps trigger sleep.

But melatonin, the "darkness hormone," is only secreted after the sun goes down—that's why night shift workers have trouble sleeping during the day, and why travelers experience jet lag. Darkness sends a signal to the body to produce more melatonin, which tells your brain it's time to get ready to sleep. Conversely, a strong light signal during the day reverses the process—as melatonin declines, cortisol and other hormones are released, raising blood pressure and core body temperature.

Sleep Solution: Melatonin Supplements

Scientists think that people who suffer from insomnia may have low levels of melatonin, and in studies, melatonin supplements have helped. Scientists at the MIT Clinical Research Center in Boston, for example, showed that oral doses of melatonin can put people to sleep, suggesting that the hormone offers an alternative to sleeping pills. In the study, participants were given melatonin and asked to close their eyes while holding a switch in a dark room. Researchers measured the time it took for the participants to release the switch, an indication that they'd fallen asleep. They fell asleep more quickly, and slept longer, than those who were given a placebo.

More good news: You only need a small amount of melatonin to reap the sleep benefits. Researchers found that people who took as little as 0.3 milligrams of melatonin got about a half-hour more snooze time. In fact, too much can disrupt your slumber.

If you've been plagued by insomnia for several weeks, and adopting good sleep habits hasn't seemed to help, a melatonin supplement may be for you. Experts recommend a dose of 0.3 to 5 milligrams orally each day for more restful nights.