Psychology explains why people sleep with a light on

The habit of sleeping with a light on, whether from a lamp, television, or hallway illumination, is common and driven by various psychological factors, according to sleep psychology.

These motivations often include a fear of the unknown, which triggers anxiety and a need for security, or difficulty managing intrusive thoughts before sleep. For some, it may also be linked to sleep disorders like insomnia or apnea.

From a biological standpoint, artificial light interferes with the body's circadian rhythm. María José Martínez Madrid, coordinator of the Chronobiology working group at the Spanish Sleep Society, explained that even low-intensity light confuses the brain, suppressing the production of melatonin. This hormone is crucial for deep, restorative sleep; without it, sleep becomes superficial and fragmented, leading to frequent awakenings.

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The presence of artificial light, even at low intensity, confuses the brain by inhibiting the production of melatonin.

Specialists warn that even light filtered through eyelids can disrupt the sleep cycle. Briefly turning on a light, such as when going to the bathroom, can interrupt the biological rhythm by eliminating existing melatonin, making it harder to fall back into deep sleep. Using low-intensity flashlights is recommended to minimize light interference.

The consequences of ignoring these sleep hygiene guidelines extend beyond daily fatigue. Chronic sleep deprivation is linked to cognitive deficits, attention problems, and an increased risk of accidents. Long-term, inadequate light exposure at night is associated with metabolic conditions like obesity, cardiovascular diseases, and mental health disorders. Emerging research also connects this habit to neurodegenerative diseases such as Alzheimer's and Parkinson's, underscoring the importance of total darkness for overall health.

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The darkness is essential, especially for young people, who show greater sensitivity to light stimuli.