evidence: This kind of behavior is cause for serious concern and falls outside the realm of the normal teenage development. You need to find out whether your child has undergone some kind of trauma (bullying, rape) or is abusing drugs or alcohol. This behavior could also indicate the beginning of a serious mental health issue such as depression, schizophrenia or bipolar disorder, all which become more common in the late teens and early 20s. [...] - Seek professional help from a qualified clinician. Begin by calling your child’s pediatrician and describing their behavior in detail. [...] - Work with your child to get professional help and explain that seeking help isn’t a sign of weakness.