Predictors of response to antidepressants - General principles and clinical implications

What variables predict who should be treated with antidepressants and who should not? if someone should be treated, what variables predict which treatment is most likely to work? If patients are treated, what predicts who will respond and who will not? Clinicians have asked these questions ever since researchers established that antidepressants were superior to placebo in the treatment of depression. Innumerable reports claim either biologic or psychosocial predictor variables of response, and every few years yet another review of predictors is published in the literature [1-4]. Although a few predictors have stood the test of time, most have been only of academic interest. Why has the enterprise of finding clinically useful predictors been minimally successful despite such intense effort? This article reviews methodologic issues that have been neglected in the pursuit of predictors to antidepressant response and proposes improved requirements for predictor research that impact clinical practice.