Depression is a disorder that occurs when there is a deficiency of 5-HT, which creates good moods. Researchers in Australia have found that the brain’s 5-HT conversion is lowest in winter. The rate of 5-HT production in the brain is directly related to the effective time of sunlight exposure. Dr. Kristen Boschwa et al. of the Baker Heart Institute in Melbourne measured cerebral blood flow directly and found that 5-HT conversion was higher during high light levels than during cloudy weather. Therefore, sunlight walking can be a good exercise for people with low mood, which can increase the time of sunlight exposure and have enough to relax the body and mind.