The pattern for most diseases is clear: the richer and more developed the country, the better the patient outcome. Schizophrenia appears to be different.

This paradox first came to light 40 years ago. Studies from Mauritius and Sri Lanka appeared to show better outcomes than developed countries: patients experienced fewer delusions and hallucinations, less disorganized speech, and improved social functioning. But these studies lacked standardized diagnostic criteria and assessment methods, and had varying attrition rates.

In the late 1960s, in an effort to standardize research methods, the World Health Organization (WHO) launched the first of the following three landmark international studies: the International Pilot Study of Schizophrenia (IPSS); the Determinants of Outcomes of Severe Mental Disorders (DOSMeD); and the International Study of Schizophrenia (ISoS).