People experiencing jet lag may turn to melatonin to reset their internal clock.

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Melatonin as a Sleeping Aid

In the United States, melatonin is available as an over-the-counter, natural sleep aid (in Europe, it requires a prescription). Many swear by its effectiveness, particularly those who use it when traveling to different time zones and shift workers who sleep during the daytime. Dig deeper, and you'll find melatonin mentioned as a veritable wonder drug, something that could potentially treat headaches, glaucoma, high blood pressure, inflammatory bowel disease, HIV/AIDS and cancer. In some animals, it has even postponed signs of aging [sources: Medline Plus; CNRS]. All that, and it's natural? Pretty amazing, right?

Not so fast there, sleepyhead. The use of melatonin supplements as a sleeping aid doesn't hold up to the scrutiny of clinical studies. In numerous reviews, researchers have noted that if melatonin does increase the amount of time that a person spends asleep, it's only by a few minutes, a clinically insignificant amount [sources: Bakalar; Buscemi et al.]. It might slightly help those who are confused about whether it's night or day, like shift workers or time zone travelers, but even then, the evidence is minimal.

It's possible that melatonin performs in clinical studies the way your car performs when you take it to the mechanic -- it suddenly refuses to make that scary noise it's been making for days. Just because melatonin's effectiveness hasn't been proven in clinical studies, should we worry about taking something that our body makes naturally? After all, the most common side effects are very similar to those you'd have when you can't sleep anyways; they include headaches, dizziness, nausea and drowsiness. Most of the studies, even when they can't show efficacy, point out that short-term use of melatonin appears to be safe for most people.

However, those same studies include the disclaimer that almost nothing is known about long-term use of melatonin (the hormone was first identified in 1958). Side effects can be more severe for some people, extending to symptoms include depression and anxiety. And the supplements are especially dangerous for some people. The following are advised to avoid melatonin:

  • children
  • pregnant and nursing women
  • asthma sufferers whose symptoms get worse at night [source: O'Neil]
  • people taking anticoagulants or those at risk for blood clots
  • people with a history of seizures. In some studies, melatonin seems to reduce the risk of seizures, while in other instances, it seems to raise it [source: Medline Plus].

If you decide to take the supplement, be aware that the optimal dosage varies from person to person, as does the proper time to ingest it. Consult your doctor before using melatonin; it's possible that your sleep problems could be aided by something that is better understood.