Melatonin is marketed both as a drug and a dietary supplement. Its indication as a drug is for insomnia in patients over 55. Trials indicate efficacy of questionable clinical relevance (sleep latency is reduced by 8 minutes). There is no evidence that melatonin is effective in reducing sleep latency in adults with circadian rhythm disorders. Evidence of efficacy is scarce and inconsistent with regard to use in children with delayed sleep disorders or attention deficit and hyperactive disorder. In children with disorders affecting neurological development, modest efficacy has been observed. It is not clear what the most appropriate dose is.