- treatment resistance: at least two serotonin reuptake inhibitors (SSRI´s), or one SSRI and clomipramine in sufficient dosages for at least 10 weeks, an augmentation trial with lithium, buspirone or a neuroleptic lasting at least 10 weeks, and complete cognitive-behavioral psychotherapy, including "exposure and response prevention" of a minimum of 20 sessions with a documented lack of efficiency