[Medical Q&A] Is melatonin a “magic drug” for insomnia?

Planner: Chinese Medical Association

Reviewer: Tian Jinzhou, Chief Physician, Dongzhimen Hospital, Beijing University of Chinese Medicine

In recent years, melatonin has been widely used to treat insomnia. In fact, melatonin is currently mainly used to treat age-related insomnia, improve sleep-wake disorders caused by jet lag, sleep-wake phase delay disorders and other circadian rhythm disorder sleep-wake disorders, as well as shift work-related reactions. The "Guidelines for the Diagnosis and Treatment of Insomnia in Adults in China" points out that melatonin sustained-release tablets can improve the sleep quality of insomnia patients over 55 years old. Exogenous melatonin can not only promote sleep onset and maintenance of sleep, but also regulate the circadian rhythm phase (including the rhythm of melatonin itself), which can be induced by physiological doses, that is, 0.1-0.3 mg to promote sleep, and 0.3-0.5 mg to regulate the circadian rhythm phase.

The natural melatonin in the human body is a hormone synthesized by the pineal gland using tryptophan. It is secreted into the blood and cerebrospinal fluid and participates in regulating the sleep-wake cycle. It has a significant circadian rhythm, and the plasma concentration of melatonin at night is at least 10 times that of the daytime concentration. Melatonin secreted at night helps to induce and maintain sleep. However, the secretion of melatonin in the human body changes with age. It begins to be secreted at 3 to 4 months after birth. The nighttime concentration reaches the highest value at 1 to 3 years old, and then slowly decreases to a plateau in early adulthood. It will continue to decline, and the peak melatonin concentration at night can be lower than 1/4 of the peak in youth at the age of 70. Therefore, many elderly people will experience age-related insomnia (such as waking up easily at night, decreased sleep efficiency, etc.). For this group of people, the dose of melatonin supplementation should just make up for the dose of their age-related secretion decrease, which can help improve sleep.

However, it should be noted that melatonin exceeding physiological concentrations can lead to daytime sleepiness, physical and mental impairment, hypothermia, and hyperprolactinemia. Therefore, it is recommended to use a lower, physiological dose (0.1-0.5 mg) of melatonin when treating insomnia and improving jet lag. However, melatonin should not be abused to avoid adverse reactions.