Characteristics of schizophrenic and depressed patients excluded from clinical research.

The process of selecting patients for research studies introduces factors that can bias outcome. The authors compared schizophrenic and depressed patients accepted for studies on their clinical research unit with patients admitted to the hospital with the same diagnoses. They found significant differences between the two groups in age, sex, and legal status. The authors conclude that many research populations may not be representative of general patient populations for a number of reasons and argue that research studies also need to focus on patients who do not meet research ward criteria.