A recent study has found that if people sit under a lamp and don't sleep in the early hours of the morning, their immune capacity will significantly decline. Because when the human body falls asleep at night, the pineal gland in the human brain secretes a large amount of melatonin. This hormone is secreted most vigorously from 11 p.m. to the early morning of the next day, and stops secreting when there is light at dawn. The secretion of melatonin can inhibit the excitability of the human sympathetic nerve, and has functions such as lowering blood pressure, slowing heart rate, enhancing the body's immunity, eliminating fatigue, and killing cancer cells. However, the most distinctive feature of the pineal gland is that as soon as the eyeball comes into contact with a light source, the secretion of melatonin stops, which affects the body's immune function. Therefore, medical experts suggest that people should try to turn off the lights when going to bed at night.