In this project we investigated the difference between efficacy (treatment outcome investigated in randomized clinical trials, RCTs) and effectiveness (treatment outcome when these treatments are applied in daily psychiatric practice) for major depressive disorder. Treatment outcome and patient features in daily practice were assessed with routine outcome monitoring. We found that effectiveness is significantly lower than efficacy. In RCTs, a stringent patient selection is applied bij inclusion/exclusion criteria. We found that patients in daily practice do differ significantly from participants in RCTs with respect to baseline severity, comorbid disorders, suicidality and employment status. However, we found that these differences have very little influence on treatment outcome. In other words, if, hypothetically, only patients who are eligible for participation in RCTs for major depressive disorder would be tre ated, treatment success would not improve dramatically.UBL - phd migration 201