Developmental Disorders Developmental disorders are mental illnesses that strike early in life. They are diagnosed in infancy or childhood. These include attention-deficit hyperactivity disorder, autism, learning disabilities, and mental retardation. Dissociative Disorders this unique and often bizarre category includes an interruption or dissociation of consciousness. If you suffer from a dissociative disorder, you may have trouble with your memory or identity. These disorders include multiple personality disorder (now known as dissociative disorder) and depersonalization disorder. Brain damage can occur in a variety of ways, but is considered to be any type of injury to the structure of the brain that disrupts or prevents normal brain function or healthy brain development. Brain damage can occur after birth (acquired, non-traumatic or traumatic brain injuries) or before birth (congenital brain injuries). Most brain damage that occurs after birth is due to an injury of some sort.