Melatonin for Insomnia: A Concise Review
Melatonin is effective for insomnia and circadian rhythm sleep disorders.
Posted May 04, 2019
Melatonin, a naturally occurring hormone that regulates sleep, is an effective and safe treatment of chronic insomnia and insomnia caused by jet lag or shift work. Sustained-release preparations of melatonin are most effective for improving the duration of sleep, whereas immediate-release forms of melatonin are best for individuals who have difficulty falling asleep. A meta-analysis of 17 double-blind, controlled studies involving a total of 284 patients concluded that taking melatonin at bedtime decreases the time required to fall asleep and increases total sleep duration (Brzezinski et al., 2005). In cases of abnormal low levels of melatonin, doses that replace normal physiological levels of melatonin (0.3 mg) improve restful sleep in the middle part of the sleep cycle. In contrast, higher doses (3.0 mg) improve sleep quality but are sometimes associated with an abnormal low body temperature (i.e., hypothermia), elevated daytime melatonin levels, and residual morning grogginess (Zhdanova, Wurtman, Regan, Taylor, Shi, & Leclair, 2001).
Taking controlled-release melatonin 2 mg together with a benzodiazepine such as diazepam (Valium™) or clonazepam (Klonopin™) significantly improves sleep time and uninterrupted sleep in elderly individuals with low serum melatonin levels (Garfinkel, Laudon, & Zisapel, 1997). In view of the high risk of falling when the elderly get up in the middle of the night, it is reasonable to substitute melatonin for a prescription sedative-hypnotic drug in this population, with the goal of reducing the number of middle awakenings. Double-blind studies demonstrate consistent improvements in sleep quality and duration, and more rapid sleep onset in individuals with chronic insomnia who take melatonin at doses between 0.3 and 3 mg (Kayumov et al., 2001).
Melatonin is beneficial in resynchronizing the sleep-wake cycle back to a rhythm that matches the normal cycle with respect to a particular time zone. A systematic review of 10 double-blind, placebo-controlled studies concluded that melatonin was effective in jet lag at doses of 0.5 to 5.0 mg when taken close to bedtime in the country of destination (Herxheimer & Petrie, 2002). The overall efficacy of melatonin was relatively less for westward flights and relatively greater when more time zones were crossed. Melatonin can be used to regulate sleep in both phase-delay and phase-advance circadian rhythm sleep disorders. In phase-advance insomnia, an individual rises early and goes to sleep early with respect to his or her home time zone. In this case taking melatonin at a dose of 0.5 mg can incrementally delay the onset of sleep over several days if taken during middle awakenings and at the time of rising in the early morning. In contrast, in phase-delay insomnia, an individual goes to sleep late and awakens late. In this case taking melatonin 0.5 mg about 7 hours after sleep onset will incrementally advance the individual to a normal sleep-wake schedule over several days. Early morning bright light exposure can be safely combined with melatonin taken at bedtime in the management of circadian rhythm sleep disturbances.
Daytime use of melatonin should be avoided (except when treating a sleep disturbance caused by circadian phase advance—see above) because of the risk of impaired cognition, which may affect work performance, reduce response time, and slow problem solving (Rogers, Dorrian, & Dinges, 1998). Melatonin is generally safe when taken at recommended doses. Uncommon mild side effects of melatonin include headache and itching.
To find out about the evidence for a variety of complementary and alternative treatments of insomnia read my book Insomnia: The Integrative Mental Health Solution.