Light at night (LAN) refers to the use of artificial or natural light during nighttime hours for visibility purposes.
Deprato et al. (2025) reports that approximately 80% of the global population is exposed to light-polluted skies, and LAN is now considered a major environmental pollutant. Sources include streetlights, vehicles, homes, industries, and even atmospheric reflections.
LAN disrupts the body’s circadian rhythm, the internal 24-hour clock regulated by the brain’s suprachiasmatic nucleus. When artificial light interferes with natural dark–light patterns, it delays the circadian clock and sleep-wake cycle, leading to melatonin suppression, sleep disturbances, and an increased risk of various diseases (Deprato et al., 2025). Blue-rich and bright LED lights cause the most significant disruption (Deprato et al., 2025). The study reports that LAN exposure is linked to higher rates of depression, bipolar disorder, anxiety, and other severe mental disorders, likely due to circadian misalignment, sleep deprivation, and changes in brain chemicals such as serotonin and dopamine.
Implications:
1.The findings suggest that light pollution and artificial light exposure at night are not only environmental/visual concerns but also have mental health implications.
2. Encourages rethinking nighttime habits — including screen use before bed, bedroom lighting, blackout curtains, and managing exposure to streetlights or indoor lights at night.
3.The implications of light at night may vary by culture or by groups
4. Designing homes and neighborhoods that minimize intrusive nighttime lighting in bedrooms, promoting lighting standards that consider human health
Prevention/ Mitigation strategies
1.Reduce screen time before bed: Use “night mode” or blue-light filters on devices, dim the brightness, and avoid stimulating content.
2. Improve bedroom lighting: Use blackout curtains, turn off or dim indoor lights, remove bright electronic indicators, and opt for warm, low-intensity lighting in the evening.
3. Maintain a consistent sleep–wake schedule: Even if artificial light is present, a regular circadian rhythm helps mitigate disruptions.
4. Use lighting design for sleep: In the evening, switch to warmer (red/orange) wavelengths; avoid bright overhead white/blue light late at night.
5.Monitor and adjust ambient outdoor lighting: If streetlights are intrusive, consider using blackout curtains or an eye mask; if indoor lighting spills into the night, turn off non-essential lights.
Source: https://doi.org/10.1016/j.scitotenv.2025.179188
