Complications!
There are certain disease naturally prone to children upto adolescent age, Most probably they suffer from Respiratory tract infection , Gastro-intestinal tract infection, worm infection, Nutritional problems, obesity, urinary tract infection, pediatric complaints like fever, diarrhea, cough, cold, asthma and Vomitting and also MENTAL & PHYSICAL GROWTH DELAY too, and that is the only reason why children cry in their early stage of life.