What is the Origin of Melatonin Onset Dim Light?

This concept is a foundational measurement in chronobiology and sleep medicine, developed to provide an objective, phase-specific anchor for the circadian system. The measurement is performed under dim light conditions because any bright light exposure would suppress melatonin synthesis, skewing the result. The DLMO is a far more accurate representation of the body's internal time than simply asking a person when they feel tired.

What is the Mechanism of Melatonin Onset Dim Light?

The suprachiasmatic nucleus (SCN), the master clock, inhibits the pineal gland during the day. As light levels decrease in the evening, the SCN releases this inhibition, allowing the pineal gland to synthesize and secrete melatonin from its precursor, serotonin. The DLMO marks the moment this suppression is lifted, signaling the start of the biological night and initiating the cascade of physiological changes necessary for sleep and nocturnal repair processes.

Melatonin Onset Dim Light ∞ Area

Melatonin Onset Dim Light

Meaning

Melatonin Onset Dim Light (DLMO) is the precise physiological marker representing the time when the pineal gland’s production of the sleep-regulating hormone melatonin begins to rise under conditions of dim light. Clinically, the DLMO is considered the most reliable indicator of an individual’s internal biological night and the phase of their circadian clock. Determining this timing is essential for chronotherapy and accurately scheduling sleep, light exposure, and medication.