The other major group in defining mental illness, is psychosis, with the major illness being schizophreina. Schizophreina is defined as a clusture of servere and prolonged mental disturbances that disrupt normal thought, speech and behaivor. It is not a "split personality" as so many people confuse it with. (Split personality disorder is actually a very rare disorder.) People with schizophrenia experience many intense sypmtoms, such as delusions, hallucinations, disorganized speech, irrational or catatonic behaivor: stupor, ridgity, or floppiness of limbs, inaction, silence, and loss of will. There are many antipsychotics used to treat shizophrenia, many of them outdated with the creation of newer and better drugs. Two of the newest and most frequently used are Risperdal and Clozaril.