Study Links Artificial Night Lighting to Increased Depression in Tree Shrews

A new study published in PNAS has revealed that chronic exposure to artificial light at night (LAN) can induce depression-like behaviors in tree shrews, mammals closely related to humans. Conducted by researchers from the University of Science and Technology of China and other institutions, the study exposed tree shrews to blue light for two hours nightly over three weeks, resulting in significant signs of depression, such as reduced sucrose preference and impaired memory. The team identified a new visual circuit where specialized retinal cells communicate with the perihabenular nucleus, a region linked to mood regulation. Silencing these neurons prevented the onset of depressive behaviors, suggesting potential long-term genetic changes. This research underscores the psychological risks of increased artificial lighting in contemporary life and opens pathways for targeted interventions to mitigate its adverse effects on mental health.