Being crazy all the time may mean that the patient is suffering from a mental disorder. Mental disorders may be caused by organic causes, that is, physical diseases, such as post-traumatic brain injury, brain tumors, mental retardation, and phenylketonuria. There are also drug and alcohol addicts who may exhibit symptoms of insanity. These can be diagnosed by detailed history taking as well as physical examination, neurological examination, and necessary laboratory and instrumental tests. If organic causes of madness are ruled out, this symptom can be considered to be caused by a functional psychiatric disorder. For example, schizophrenia and affective disorders can be diagnosed by detailed psychiatric examination.