Sun Science: Why Sunny Days Feel Good

Author: Sam Marchetti

Warmer months of the year. The days get longer, the temperature rises, and nature starts to bloom once again. Spring just naturally feels good, and maybe the most notable part of it is the fact that after months of cold and darkness, we finally get more sunshine! More importantly though, everyone’s mood seems to improve (at least somewhat).

Most people would probably attribute sunshine-induced good vibes to having more vitamin D from soaking up the Sun’s rays. Vitamin D is responsible for a lot of different things in the body, from lowering our risk of cancer and cardiovascular disease to preventing depression, although primarily it’s known to be responsible for our bone health.¹ While it’s true that sunlight converts a specific chemical in our skin (called 7-dehydrocholesterol, if you were curious) into vitamin D, the good vibes don’t just stop there!²

Sunlight also stimulates the release of a very important hormone called serotonin—also known as the happy hormone! Serotonin acts as a stimulant for many pathways in the brain, by positively impacting mood, memory, appetite, pain, fear, and sleep, among other things.³ At nighttime, serotonin is converted into melatonin, which you might recognize as something you or someone you know takes as a sleep aid.⁴ When the days get longer and we get more exposure to sunlight, melatonin levels go down and serotonin levels in our brains have been observed to rise, which in turn makes us feel more calm, relaxed, and happy.⁵

How exactly this happens, though, is up for a bit of debate. There is some evidence that serotonin release is actually triggered when sunlight hits our retinas (the back of our eyeball), and not our skin! ⁶ This is because serotonin is considered an important part of our retinal function, and keeps our eyes working properly. ⁷

However, there’s not enough research in the area to say this with certainty—but still just remember to not look directly at the Sun. Other studies suggest that serotonin is released when sunlight interacts with specific proteins in our skin. ^8,9 Simply put, although we’re not exactly sure how sunlight causes our bodies to release serotonin, we know with near-certainty that it does.

Beyond putting us in a good mood when we’re in the Sun, sunlight can have positive effects on learning and brain function! For example, sunlight has been shown to decrease the risk of cognitive (brain processing) impairment in people living with depression. ¹⁰ This is because the interaction of sunlight in our retinas activates learning in our brains and also contributes to our mood! ¹¹

With the peak of summer, the extra rays of sunshine are a welcome gift. We feel like spending more time outside, like moths to an (admittedly massive) flame, and as long as we remember to wear sunscreen, our bodies will thank us. After spending some time in the sun, despite how hot it may feel, rest easy knowing that it’s doing its best to keep you happy and healthy.

1. Wacker, Matthias, and Michael F. Holick. “Sunlight and Vitamin D.” Dermato-Endocrinology 5, no. 1 (January 5, 2013): 51–108. https://doi.org/10.4161/derm.24494. 

2. Wacker, “Vitamin D”.

3. Bamalan, Omar A., Marlyn J Moore, and Yasir Al Khalili. “Serotonin.” Essay. In National Library of Medicine, n.d. https://www.ncbi.nlm.nih.gov/books/NBK545168/.

4. Mead, M. Nathaniel. “Benefits of Sunlight: A Bright Spot for Human Health.” Environmental Health Perspectives 116, no. 4 (April 2008): A169–A167. https://doi.org/10.1289/ehp.116-a160.

5. Lambert, GW, C Reid, DM Kaye, GL Jennings, and MD Esler. “Effect of Sunlight and Season on Serotonin Turnover in the Brain.” The Lancet 360, no. 9348 (December 7, 2002): 1840–42. https://doi.org/10.1016/s0140-6736(02)11737-5.

6. Sansone, Randy A, and Lori A Sansone. “Sunshine, Serotonin, and Skin: A Partial Explanation for Seasonal Patterns in Psychopathology?” Innovations in Clinical Neuroscience 10, no. 7–8 (July 2013): 20–24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3779905/.

7. Mead, M. Nathaniel. “Benefits of Sunlight: A Bright Spot for Human Health.” Environmental Health Perspectives 116, no. 4 (April 2008): A169–A167. https://doi.org/10.1289/ehp.116-a160.

8. Sansone, “Seasonal Patterns”.

9. Gambichler, Thilo, Armin Bader, Mirjana Vojvodic, Falk G Bechara, Kirsten Sauermann, Peter Altmeyer, and Klaus Hoffmann. “Impact of UVA Exposure on Psychological Parameters and Circulating Serotonin and Melatonin.” BMC Dermatology 2, no. 1 (April 12, 2002). https://doi.org/10.1186/1471-5945-2-6.

10. Kent, Shia T, Leslie A McClure, William L Crosson, Donna K Arnett, Virginia G Wadley, and Nalini Sathiakumar. “Effect of Sunlight Exposure on Cognitive Function among Depressed and Non-Depressed Participants: A Regards Cross-Sectional Study.” Environmental Health 8, no. 1 (July 28, 2009). https://doi.org/10.1186/1476-069x-8-34.

11. Fernandez, Diego Carlos, P. Michelle Fogerson, Lorenzo Lazzerini Ospri, Michael B. Thomsen, Robert M. Layne, Daniel Severin, Jesse Zhan, et al. “Light Affects Mood and Learning through Distinct Retina-Brain Pathways.” Cell 175, no. 1 (September 20, 2018). https://doi.org/10.1016/j.cell.2018.08.004.