<qa>  What is the focus of the current study on regression in core symptoms of autism?- Regression is defined as: Language loss: Loss of at least 3 spontaneously meaningful words excluding mama or dada used for at least a month, and lost for at least a month.ANDOR Nonverbal communicationsocial loss: Loss of more than one nonverbal communicative behavior e.g. gestures, joint attention, eye contact, imagination, pretend play, sharing, showing, watching children, orienting to name, social smiling, social games, spontaneous imitation of actions, response to social overtures. Although there is overlap in the age period for regression specified in this protocol regression between 15-30 months and that described for childhood disintegrative disorder CDD the DSM-IV criteria for indicate apparently normal development for the first 2 years after birth , the criteria for CDD also indicate a diagnosis can only be made if symptoms are not better accounted for by another pervasive developmental disorder such as autism. Symptoms of CDD that separate it from autism include loss of acquired skills in areas such as motor skills and bowel or bladder control, while the focus of the current study is on regression in core symptoms of autism i.e. socio-communicative skills. Thus, the currently protocol will include children with regression over 2 who meet criteria for autism, but not those who only meet criteria for CDD. 