 This subdivision is based on presence of at least six out of nine long @-@ term ( lasting at least six months ) symptoms of inattention , hyperactivity – impulsivity , or both . To be considered , the symptoms must have appeared by the age of six to twelve and occur in more than one environment ( e.g. at home and at school or work ) . The symptoms must be not appropriate for a child of that age and there must be evidence that it is causing social , school or work related problems . 
