Neurobiological disorder: An illness of the nervous system caused by genetic, metabolic, or other biological factors. Many illnesses categorized as psychiatric disorders are neurobiological, including autism, bipolar disorders, obsessive-compulsive disorders, schizophrenia, and Tourette syndrome. Neurobiology is a subspecialty within the fields of both biology and neurology. It is the study of the cells of the nervous system and their organization as a system that regulates behavior and processes information. Neurobiological disorders are diseases that involve the functioning of the nervous system. Symptoms of these disorders usually involve the inability to regulate behavior; for example, people with schizophrenia act out in bizarre ways, and epileptics cannot control their falling. Sometimes symptoms have to do with the processing of information; for example, people with attention deficit disorder/hyperactivity have problems concentrating and organizing complex tasks. Doctors recognize hundreds of neurobiological disorders, such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, autism, depression, cerebral palsy, multiple sclerosis, bipolar and obsessive/compulsive disorders, and many others. They affect the function of the brain and may have their origin in the brain itself. They are considered to be caused by certain combinations of genetic, environmental and metabolic factors. Neurobiological disorders are also called neurological disorders