Can Watching TV at Night Affect Your Mood?

As light is the most potent zeitgeber, could nighttime exposure to light alter circadian rhythms and mood that are entrained to environmental light-dark cycles? For 1 month at night, female hamsters were exposed to darkness, dim blue light (wavelength peak, ~480 nm), dim white light (broad spectrum, including blue), or dim red light (wavelength, >600 nm).

Blue or white light exposure, compared with darkness, led to more depressive and anhedonic behaviors (e.g., immobility in the forced swim test, decreased preference for sucrose) and lower spine density on hippocampal neurons. In a separate experiment, brief nighttime exposure to blue or white light induced more c-Fos activity in the suprachiasmatic nucleus than red light or darkness.