What Role Does Sunlight Play in Our Mood?

Sunlight helps us see and is responsible for the regulation of our sleep cycle. According to brainfacts.org, “Recently, researchers at the National Institute for Mental Health (NIMH) found light affects brain areas that regulate mood. ”

There are three kinds of cells that respond to light hitting the retina: rods, cones, and ipRCGs (intrinsically photosensitive retinal ganglion cells). ipRCGs contain a protein that is light sensitive known as melanopsin. Through ipRCGs, light is able to “reach and affect the brain’s mood-regulating areas via the ipRGCs, projecting from the retina to the peri-habenular region, to the nucleus accumbens and the ventromedial prefrontal cortex (vmPFC). " The structures mentioned are involved with emotions and decision making. Also, ipRCGs regulate functions not regarding images, such as adjusting our circadian rhythms (internal biological clock).

This link can help better understand SAD which stands for Seasonal Affective Disorder. It was thought that Seasonal Affective Disorder occurred because of a circadian clock disruption. "When you live in an area with a shorter day length, the total day/night length is still 24 hours. You haven’t traveled between time zones, so the circadian clock should still be attuned to the light-dark cycle, even with less light. ” There has been a study on mice and the results were that there had been mood changes two weeks after a disruption in their light environment. This can provide an explanation for the changes in mood from light to take effect in a period of time in people with SAD. Studies have shown that light therapy can be a treatment for people with SAD as well as "people suffering from general depression and bipolar disorder. ”