Sudden crying during sleep can be caused by physiological or pathological factors, such as nightmares, hunger, etc. Pathological factors, such as colic, tuberculosis, etc., can cause infants and young children to cry suddenly during sleep. 1. Physiological factors: infants and young children will also have dreams, when there are nightmares, it will make infants and young children instinctively feel insecure, showing the phenomenon of sudden crying; at the same time, feeling hungry during sleep will also cause infants and young children to feel uncomfortable, and suddenly cry. 2. Pathological factors: infants before half a year old, due to the imperfect development of the digestive system, prone to intestinal colic, so that infants feel abdominal pain, resulting in sudden crying; a little bit older children, due to bone tuberculosis, the relevant tissues in the night time pain, showing the symptoms of night crying. Babies suddenly cry in their sleep, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.