Objective: The invesitagtors' primary objective is to establish whether a predictive score based on a pre-determined set of clinical variables and biomarkers differentially predicts response to antidepressant medication and to cognitive-behavioural psychotherapy with a clinically significant effect size. Secondary objectives include testing each predictor separately, testing a gene-environment interaction between the serotonin transporter polymorphism and childhood maltreatment, and integrative analyses using multiple predictors to derive optimized prediction algorithms.