A new study has revealed that prolonged exposure to artificial light at night can trigger depression-like behavior by activating certain neural pathways in the brain.
The study, conducted in shrews, diurnal mammals genetically related to primates, provides important insights into how light at night can disrupt mood regulation. The results are published in the journal Proceedings of the National Academy of Sciences .
The research team in the study, led by researchers from the University of Science and Technology of China, the Kunming Institute of Zoology under the Chinese Academy of Sciences, and Hefei University, exposed tree shrews to blue light for two hours each night for three weeks.
After this period of exposure, the animals then showed clear symptoms resembling depression, including a 20 percent decrease in preference for sucrose, reduced exploratory behavior, and impairment in long-term memory.
Using sophisticated neural tracing techniques, researchers identified previously unmapped visual circuits. Specialized retinal ganglion cells were revealed to send signals directly to the perihabenular nucleus. (pHb), which then projects those signals to the nucleus accumbens, a key center in the brain involved in mood regulation.
Specifically, when pHb neurons were chemically silenced, the mice no longer exhibited depression-like behavior in response to light exposure at night. Further analysis through RNA sequencing techniques that these changes correlated with the activity of genes associated with depression, indicating potential long-term effects.
As light pollution and screen exposure become more prevalent in modern life, this research raises important questions about the impact of artificial lighting on psychological health and its implications for modern lifestyles.
"These findings provide us with both a warning and a road map," said Yao Yonggang, a professor at the Kunming Institute of Zoology. "The same light that keeps us productive at night may be subtly reshaping the brain circuits that regulate mood, but now we know where to look for solutions."
The findings open new avenues for targeted interventions that could reduce the psychological impact of artificial light, while maintaining its benefits to society, the study said.
