Sleeping with the lights on at night has adverse effects on babies because the human body has a normal circadian rhythm related to light. When the day is bright for activity, darkness at night for sleep, light on the body’s hormone secretion will have a greater impact, especially melatonin. Melatonin is secreted at its peak between two and three o’clock at night, which can delay aging, antioxidant and regulate immunity, and is an essential and important hormone for the human body. If you sleep with the lights on for a long time, young babies may be affected by melatonin secretion, causing developmental problems in babies, and can also have a negative impact on the baby’s sleep rhythm and sleep quality. This can lead to easy awakening, crying, and more infections and respiratory and lung diseases than babies of the same age.