We’ve all witnessed the rejuvenating effects of a sunny day. According to Marie-Annette Brown, PhD, RN, author of When Your Body Gets the Blues, sunlight can affect our mood. Sunscreen shields your skin from these happy UV rays — however, you should still apply SPF if you’re going to be outdoors for more than 10 minutes. Light that enters our eyes has a more immediate impact, increasing levels of serotonin in the brain. Dr. Brown recommends going for a 20-minute walk during the brightest part of the day at least five times a week. If you can’t get outdoors, sitting by a sunny window can help. Or consider using a light therapy device for 30 minutes each morning. Look for a 5,000 lux blue LED lamp or a 10,000 lux white fluorescent light with a wavelength of approximately 460 nanometers.