Can Watching TV at Night Affect Your Mood? Depressive and anhedonic behaviors and altered neuronal structures are found in animals exposed to blue or white light at night. 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. COMMENT Intrinsically photosensitive retinal ganglion cells (ipRGCs), which contain melanopsin, signal the suprachiasmatic nucleus to regulate circadian rhythms and limbic regions like the hippocampus. Because melanopsin is sensitive to blue but not red light, blue light led to greater effects on mood, apparently mediated by reduction by ipRGCs in hippocampal signaling and alterations of gene expression that could modify brain-derived neurotrophic factor activity. Common sources of blue light such as television and computer screens, even at the relatively low intensities in this study (150 lux), might induce changes in mood and circadian rhythms, especially in vulnerable individuals such as depressed people. Patients with persistent depression therefore might be advised not to spend too much time at night with their computers or TVs. Source: Bedrosian TA et al. Nocturnal light exposure impairs affective responses in a wavelength-dependent manner. J Neurosci 2013 Aug 7; 33:13081. (dx.doi.org/10.1523/JNEUROSCI.5734-12.2013
Posted on: Tue, 03 Sep 2013 09:10:07 +0000
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