Melatonin is a hormone produced primarily by the pineal gland. It is often referred to as the “darkness hormone” because its production is powerfully stimulated by darkness and suppressed by light. The main function of melatonin is to signal the time for sleep, regulating the 24-hour cycle of biological activities known as the circadian rhythm. When melatonin levels drop below normal, this critical signal is weakened, leading to issues related to sleep and the timing of other bodily processes.
Environmental and Behavioral Disruptors
Exposure to light, particularly in the evening, is a primary cause of low melatonin because specialized photoreceptors in the retina signal the brain’s master clock to suppress the hormone’s release. Even low levels of artificial light at night can significantly suppress melatonin secretion.
Blue light, emitted by electronic screens, LED lights, and energy-efficient bulbs, is particularly disruptive due to its short wavelength and high energy. Exposure to blue light can delay the onset of melatonin synthesis and shorten its duration in the body. This is why using electronic devices close to bedtime can make it challenging to fall asleep and maintain a regular sleep pattern.
A lack of consistent timing and routine can also confuse the body’s internal clock, leading to lower melatonin levels. Irregular sleep schedules, such as those caused by jet lag or rotating shift work, disrupt the synchronization of the circadian rhythm. Night shift workers, for example, consistently exhibit lower melatonin levels because they are exposed to light during their biological night.
Ambient light pollution during the night, even while a person is attempting to sleep, can interfere with production. The low light intensities of urban skyglow can be enough to suppress melatonin. This constant illumination can prematurely halt the full nocturnal release, leading to a shorter and less pronounced melatonin peak.
Age-Related and Biological Changes
Melatonin production in the pineal gland progressively declines as a person ages, becoming more pronounced after age 50. This natural decline is thought to be partly due to the calcification or shrinking of the pineal gland over time, which reduces its capacity to synthesize and secrete the hormone effectively.
The body’s stress response also plays a direct role in melatonin suppression through the hormone cortisol. Melatonin and cortisol have an inverse relationship: when one is high, the other should be low. Cortisol, the “stress hormone,” is naturally highest in the morning and should drop to its lowest levels at night.
Chronic stress keeps cortisol levels elevated into the evening, which directly inhibits melatonin synthesis and release. When melatonin production is suppressed, evening cortisol levels often remain high. Certain underlying health conditions, particularly neurological disorders and severe depression, are also associated with a pronounced decrease in circulating melatonin.
Dietary and Substance Interference
Medications
A variety of substances consumed can actively interfere with the body’s ability to produce or use melatonin. Certain classes of medications inhibit the synthesis pathway or block the receptors. Beta-blockers, commonly prescribed for high blood pressure, can significantly decrease nocturnal melatonin release by blocking the adrenergic receptors necessary for synthesis.
Other medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) and certain selective serotonin reuptake inhibitors (SSRIs), may also decrease melatonin levels. NSAIDs, such as ibuprofen, may interfere with the hormonal cascade that leads to production. Antidepressants that modulate serotonin levels can impact melatonin because serotonin is a direct precursor in the synthesis process.
Alcohol and Stimulants
Stimulants and depressants also disrupt the timing of melatonin release. Alcohol consumption, even in moderate amounts, has been shown to reduce nighttime melatonin production by up to 20%. It also fragments sleep architecture, interfering with the hormone’s role in maintaining deep sleep. Caffeine, while not directly suppressing synthesis, can delay sleep onset and disrupt circadian rhythms if consumed too close to bedtime.
Nutritional Deficiencies
A lack of essential nutritional precursors can restrict the raw materials needed for production. Melatonin is synthesized from the amino acid tryptophan, which must be obtained through the diet. This conversion process requires cofactors, such as Vitamin B6 and Magnesium, to facilitate the necessary enzymatic reactions. Deficiencies in these specific vitamins and minerals can limit the body’s capacity to manufacture sufficient quantities of melatonin.