Melatonin for Sleep - A Narrative Review

Introduction:

The melatonin hormone is secreted by the brain’s pineal gland. Melatonin production is highest at night, and light stops its production. Therefore, melatonin regulates the body’s circadian rhythm (the biological clock). Many individuals experience sleep deprivation. Hence, they use melatonin supplements to facilitate sleep.

What Are the Advantages of Melatonin Supplements?

Over the past few decades, prescriptions for sleep medications have increased manifold. As a result, patients use various medications, such as Benzodiazepines. These medications cause many adverse effects. Hence, synthetic melatonin is available as a dietary supplement for sleep disorders. It is available as tablets, capsules, lozenges, syrups, and other preparations. It is generally safe, with fewer side effects. Various advantages include:

1. Melatonin is a Food and Drug Administration (FDA) approved supplement for sleep.

2. It ameliorates sleep quality in patients with insomnia.

3. Various studies suggest a favorable profile of melatonin in jet lag patients.

4. There are no dose restrictions for melatonin. It is because it does not lead to a hangover effect or dependence.

5. Melatonin can also improve eye health due to its antioxidant effects.

What Are the Sleep Disorders for Which Melatonin Is Effective?

1. Sleep disorders comprise of:

2. Insomnia.

3. Obstructive sleep apnea syndrome (OSAS).

4. Hypersomnolence (excessive daytime sleep).

5. Circadian rhythm disorders.

6. Parasomnias (abnormal behavior during sleep).

7. Sleep-related movement disorders.

However, synthetic melatonin is approved for the management of the following conditions:

• Primary Insomnia: Primary insomnia does not occur due to an underlying condition. It is an inherent disorder. Primary insomnia remains for many years in a person’s life. It often begins during childhood. People experience a complete lack of sleep or problems falling asleep in this disorder. It is the most frequent type of sleep disorder. Patients experience irritability, frustration, daytime laziness, low energy, physical discomfort, and impaired mental functioning. Research suggests that melatonin can reduce the time it takes a person to fall asleep. But its effects on sleep quality and sleep time are unclear.

• Age-related Insomnia: Aging changes sleep regulation in many individuals. Furthermore, melatonin production decreases with age. About 30 percent of people over age 50 experience insomnia. As a result, they have decreased total nighttime sleep time, frequent awakenings, difficulty falling back asleep, and early morning awakenings. These changes are associated with increased daytime sleepiness, attention deficits, memory deficits, and mood disorders. A study suggested that 300 micrograms (µg) of melatonin given to elderly insomniacs half an hour before bedtime could improve their sleep.

• Jet Lag: Jet lag affects people while traveling across multiple time zones by airplane. People may not feel well and have disturbed sleep, daytime tiredness, impaired functioning, and digestive issues. Evidence suggests that melatonin can improve jet lag symptoms like alertness and daytime sleepiness. Melatonin is effective in preventing jet lag. Occasional short‐term use appears to be safe. It can be given to adult travelers flying across five or more time zones. Furthermore, it is recommended for recurrent jet lag. Various studies show that melatonin is effective in reducing jet lag. However, there is insufficient evidence to prove that melatonin improves sleep quality in jet lag patients.

• Delayed Sleep-Wake Phase Sleep Disorder (DSWPD): The sleep pattern in this disorder is delayed from a regular sleep pattern. It causes a person to fall asleep late at night and wake up later. Research shows that melatonin reduces the time it takes to fall asleep. It further advances the sleep initiation in adults and children with DSWPD. However, it is uncertain about the risk-benefit ratio of melatonin in these patients.

• Circadian Rhythm Sleep Disorders in the Blind: Studies reveal that there is less melatonin production in blind individuals. Furthermore, the eye lesions disrupt the biological clock in the daytime or nighttime environment. Assessment of sleep patterns in blind people shows a higher sleep disorder prevalence. In some studies, melatonin has been administered to blind subjects and compared with placebo (or no-treatment baseline). As a result, sleep parameters improve. The results suggest that prior knowledge of circadian rhythm and the timing of treatment may improve the efficacy of melatonin. Hence, melatonin can improve circadian rhythm sleep disorders in adults and children. Daily administration of synthetic melatonin is the current treatment of choice for this disorder. Melatonin is shown to rectify the underlying circadian rhythm abnormality. Also, it may improve sleep and decrease daytime napping.

• Shift Work Sleep Disorder (SWSD): Disturbed sleep and sleepiness during the job are common problems among night shift workers. Synthetic melatonin is a promising treatment option for improving daytime sleep in night workers. However, it is unknown whether melatonin can improve daytime sleep quality and duration in people with night-shift jobs.

• Pediatric Sleep Disturbances: Sleepiness in children may manifest as irritability, behavioral issues, learning difficulties, road traffic accidents (in teenagers), and poor educational performance. A majority of children with pediatric sleep disturbances respond to melatonin. A dose of one to three milligrams (mg) is given thirty minutes before bedtime. It can improve sleep onset and total sleep duration in about 80 percent of cases. Further, melatonin is well tolerated and has minimal adverse effects. However, it is recommended that parents work closely with the pediatrician before administering melatonin supplements to their children.

Oral melatonin in appropriate amounts is safe. However, side effects of melatonin include:

• Headaches.

• Giddiness.

• Nausea.

• Drowsiness.

Less common side effects include:

• Mild depression.

• Tremors.

• Anxiety.

• Abdominal pain.

• Irritability.

• Confusion.

• Disorientation.

It can also cause mild daytime drowsiness. Hence, driving or using heavy machinery is not recommended within five hours of taking melatonin. The evidence regarding melatonin as a long-term drug for sleep disorders is limited. It is mainly due to poor bioavailability, rapid metabolism, and a short half-life. To know the efficacy of melatonin in treating sleep disorders, it is important to monitor the drug after administration. Furthermore, monitoring includes adverse drug reactions such as daytime sleepiness and headaches.

Conclusion:

Insomnia is a common complaint seen in many patients. It is a safe first-line sleep aid that may promote a regular sleep cycle. As a result, many patients take melatonin as an OTC drug. However, clinicians recommend melatonin only for insomnia and jet lag disorders. Further, if a patient with insomnia does not respond to melatonin therapy, the patient should be evaluated by a psychiatrist for underlying disorders.