Evaluation of psychiatric interventions in an observational study: issues in design and analysis

Characteristics of randomized controlled clinical trials (RCTs) and observational studies of psychiatric intervention effectiveness are contrasted. Randomization drives treatment assignment in an RCT, whereas clinician and patient selection determine treatment in an observational study. Strengths and weaknesses of randomized and observational designs are considered. The propensity adjustment, a statistical approach that allows for intervention evaluation in a nonrandomized observational study, is described here. The plausibility of propensity adjustment assumptions must be carefully evaluated. This data analytic strategy is illustrated with the longitudinal observational data from the National Institute of Mental Health Collaborative Depression Study, Evaluations presented here examine acute and maintenance antidepressant effectiveness and demonstrate effectiveness of the higher categorical doses.