CIO is not recommended until at least 6 months , some people start at 4 months . But that ' s really frowned upon . For a baby to understand CIO , they have to have a basic understanding of object permanence which newborns do not . When you leave a newborn to cry , all they know is that they ' re alone in the world . They don ' t know mommy will be back later . A newborn baby does not , in any way , shape , or form have the ability or understanding to learn what you ' re trying to teach them when you let them CIO . If you leave a newborn baby to cry , all they are learning is that they can ' t count on you when they need something . Because it ' s just that , they need something . When a newborn cries , they need you . Even if it ' s just for comfort . Also , crying uses a lot of energy , so letting a newborn CIO is going to result in them needing to eat even if they previously weren ' t crying for food . Newborns know nothing , they can ' t reliably communicate , they have no control over their bodies , they are simply not capable of grasping what CIO is meant to teach . This is so true in fact , that in most States using CIO on a newborn is considered neglect .