Exposure to artificial light at night might be doing more than just disrupting your sleep—it could be impacting your mood. A new study has found that chronic exposure to nighttime light can trigger depression-like behaviors by activating specific pathways in the brain.
Researchers from the University of Science and Technology of China, along with the Kunming Institute of Zoology and Hefei University, conducted experiments on tree shrews—a type of diurnal mammal closely related to primates. They exposed the animals to blue light for two hours each night over three weeks. The results were striking: the tree shrews exhibited clear signs of depression, such as reduced enjoyment of sweet treats, less exploration, and memory problems.
The scientists discovered that specialized cells in the eyes sent signals directly to a part of the brain called the perihabenular nucleus (pHb). This region then connected to the nucleus accumbens, a key area involved in regulating mood. When the pHb neurons were chemically silenced, the tree shrews no longer showed depression-like behaviors despite the light exposure. This suggests a direct link between nighttime light and mood regulation.
With the rise of light pollution and increased screen time, especially at night, these findings raise important questions about how modern lifestyles might be affecting our mental health. The study indicates that artificial light at night could have long-term effects on mood by altering gene activity related to depression.
“These findings give us both a warning and a roadmap,” said Professor Yao Yonggang from the Kunming Institute of Zoology. “The same light that enables our nighttime productivity may be subtly reshaping brain circuits underlying mood—but now we know where to look for solutions.”
This research opens new possibilities for interventions that could reduce the psychological impacts of artificial light while maintaining its benefits. As we navigate an increasingly illuminated world, understanding how light affects our brains is more important than ever.
