Studies suggest that exposure to screen-type light from 11:00 pm to 4:00 pm activates a specific circuitry in your brain called the Hebanula, lowering dopamine and creating the feeling of disappointment and melancholy. This suggests to be one of the factors that cause and sustain MDD and spectrum disorders.
The most potent impact of light on physiology and behavioral state comes from its regulation of circadian rhythms. Mammalian physiology and behavior are coordinated by circadian clocks into rhythms that are synchronized with the light–dark cycles of a 24-hour solar day. These molecular
clocks, based on interlocked transcription/translation feedback loops, are present in most cells throughout the body and are synchronized by a ‘master’ clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. This endogenous clock is self-sustained even in the absence of external stimuli but can be entrained to light–dark cycles in a process called photoentrainment.
A change in the timing of the light–dark cycle (e.g., light exposure at night time) will result in a phase shift of circadian rhythms. Many behavioral and physiological functions such as sleep–wake regulation, hormone secretion, and thermoregulation vary across the light–dark cycle coordinated with the circadian rhythm, therefore, it is not surprising that a disruption of the circadian rhythm can impact gross physiology and behaviour.
Circadian rhythms can affect mood and the behavioral state via SCN connections to the mood regulatory centers. The SCN receives direct input from the retina and then sends signals via direct and indirect projections throughout the brain to various regions involved in the regulation of mood and behavioral state including the lateral habenula among others.
The habenula is a cellularly diverse structure located in the posterior-dorsal-medial region of the thalamus (Hu et al., 2020) and can be divided into anatomically distinct lateral and medial nuclei. Functional studies suggest that aberrant LHb activity is more closely associated with depression (Li et al., 2013; Seo et al., 2018; Yang et al., 2018b).
How is the Blue Light connected?
Not all colors of light have the same effect. Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown.
A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect, notes Stephen Lockley, a Harvard sleep researcher.
What is the solution to lower the risk of depression?
Avoid screen time from 11 pm to 4 am and get a good restful sleep.
Limit your screen time by putting away your devices 2-3 hours before bedtime.
If you are a night shift worker and cannot avoid blue light, try wearing blue light glasses which block some of the blue light.
Reduce the screen brightness in your device or use night light mode, if available.
Use a dim red light if you do use a night light when sleeping.
Expose yourself to plenty of sunlight, especially in the mornings.
Young, C., Lyons, D., & Piggins, H. (2022). Circadian Influences on the Habenula and Their Potential Contribution to Neuropsychiatric Disorders. Frontiers In Behavioral Neuroscience, 15. doi: 10.3389/fnbeh.2021.815700
Nina Milosavljevic Faculty of Biology, Medicine and Health, University of Manchester, How Does Light Regulate Mood and Behavioral State? Published: 12 July 2019
Diego Carlos Fernandez, P. Michelle Fogerson, Lorenzo Lazzerini Ospri, Haiqing Zhao, David M. Berson, Samer Hattar, Light Affects Mood and Learning through Distinct Retina-Brain Pathways, 2018, Cell 175, 71–84 September 20, 2018 Published by Elsevier Inc. https://doi.org/10.1016/j.cell.2018.08.004
Bedrosian, T., & Nelson, R. (2017). Timing of light exposure affects mood and brain circuits. Translational Psychiatry, 7(1), e1017-e1017. doi: 10.1038/tp.2016.262
Huberman, A. (2021). Find Your Temperature Minimum to Defeat Jetlag, Shift Work & Sleeplessness. Retrieved 1 May 2023, from https://hubermanlab.com/find-your-temperature-minimum-to-defeat-jetlag-shift-work-and-sleeplessness/