Randomized controlled trials in schizophrenia: opportunities, limitations, and trial design alternatives.

State-of-the art clinical trial design and methodology are enormously important for the advancement of the field. In contrast, the critical relevance of trial conduct and implementation have only more recently been the focus of discussion and research. Although randomized controlled trials are generally considered the gold standard for the assessment of pharmacologic and nonpharmacologic interventions in medicine, trials are vulnerable to complications and influences that can seriously compromise their success. Like interventions, trial design and conduct are also contextual. They need to be individualized and adapted to a number of relevant variables, such as setting, population, illness phase, interventions, patient and rater expectations and biases, and the overall aims of the investigation. While this means that there is no unified approach possible, certain general principles and guidelines require careful consideration. Knowledge of basic solutions and alternatives, and the recognition of the complex challenges that need to be addressed proactively can help to minimize unwanted outcomes, including trial failure and uninformative or falsely negative outcomes. Moreover, novel design alternatives need to be explored that target sample enrichment according to the study question and enhancement of precision in the measurement of relevant outcomes. We propose two novel design strategies that take advantage of the recently validated early antipsychotic response paradigm (that has also been observed with antidepressants and mood stabilizers). In the "early responder randomized discontinuation design" all patients are assigned to the active drug, and only those who had at least a minimal response at 2 weeks are enrolled in a double-blind, placebo-controlled discontinuation trial, enriching the placebo controlled trial portion with true drug responders. In the mirror image "early nonresponder randomized dose increase or augmentation design," early nonresponders at 2 weeks are assigned to staying on the medication or going either to a higher dose or an augmentation agent. It is hoped that through increased attention to the issues raised in this article and further refinement of trial methodology and conduct, the field will make much needed additional progress in the prevention and treatment of schizophrenia.