It is thought to be present at birth, becoming manifest in late adolescence when the prefrontal cortex matures. No one is quite sure exactly what causes schizophrenia. It may be spectrum disorder of several related conditions, or it may be a single entity. There have been several classification systems over the years. Based on outcomes and MRI scans there appears to be four or five sub-types, with different outcomes associated with different patterns of brain structure changes.
Schizophrenia is considerably more disorganizing but can be confused with bipolar disorder.
It has probably been around for a much longer time though, because it has a fairly even distribution around the world. They have had a limited success, there being few drugs disliked as much as Haldol, which was the most commonly prescribed for schizophrenia. The new atypical drugs are more effective over a broader range of symptoms with fewer unpleasant side effects. They are a major advance in the treatment of schizophrenia that is only slowly being realized. There is no cure for schizophrenia, only relief from symptoms with continued use of medication.