Randomized controlled trials in evidence-based mental health care: getting the right answer to the right question.

The purpose of clinical research is to answer this question: Would a new treatment, when added to the existing range of treatment options available in practice, help patients? Randomized controlled trials (RCTs)--in particular, double-blind RCTs--have important methodological advantages over observational studies for addressing this question. These advantages, however, come at a price. RCTs compare treatments using a particular allocation rule for assigning patients to treatments (random assignment) that does not mimic real-world practice. "Favorable" results from an RCT indicating that a new treatment is superior to existing treatments are neither necessary nor sufficient for establishing a "yes" answer to the question posed above. Modeled on an experimental design, RCTs are expensive in time and money and must compare simple differences in treatments. Findings have a high internal validity but may not address the needs of the field, particularly where treatment is complex and rapidly evolving. Design of clinical research needs to take account of the way treatments are allocated in actual practice and include flexible designs to answer important questions most effectively.