Although elderly people often have difficulty sleeping² and melatonin supplements have been shown to improve sleep in the elderly,³ melatonin secretion does not appear to decline in healthy older adults to a significant degree, despite many preliminary reports to the contrary.⁴ Most of these preliminary studies failed to verify that older subjects were healthy and not using drugs that suppress melatonin secretion (e.g., aspirin, ibuprofen, beta-blockers). Routine replacement of melatonin in elderly persons is, therefore, not recommended.

Adults with insomnia have been shown to have lower melatonin levels.⁵ Frequent travelers and shift workers are also likely to benefit from melatonin for the resynchronization of their sleep schedules,⁶ though a melatonin “deficiency” as such does not exist for these people. Patients with heart disease have been reported to have low melatonin levels, but whether this abnormality increases the risk of heart disease or whether heart disease leads to the low melatonin level is not yet known.⁷ People with schizophrenia were found to have low melatonin output and experienced significantly improved sleep following melatonin replacement supplementation.⁸