How people with major depression adjust their expectations of future life events in response to other patients’ reports of the positive effects of psychotherapy

Previous research proposed the devaluation of positive information, referred to as cognitive immunisation, as a mechanism underlying the persistence of negative expectations in depression. In a pre-registered experimental study, we tested this hypothesis by enhancing vs. inhibiting the engagement in cognitive immunisation and comparing it with a distraction control condition and a no-instruction control condition. In a sample of patients with major depression (N = 156), we presented participants with video recordings of other patients in which they reported on the positive effects of psychotherapy. Cognitive immunisation was manipulated by instructing participants to focus on similarities vs. differences between themselves and the persons from the videos. The results show that the other patients’ reports led to a significant increase in both participants’ expectations of future life events and their treatment expectations. However, there were no significant differences between the experimental conditions in expectation change, most likely because the manipulation was not powerful enough according to the manipulation check. Only in men the cognitive immunisation-promoting condition effectively blocked expectation change. This study shows that watching positive reports from other patients helps people with major depression improve their pre-treatment expectations. However, cognitive immunisation does not modulate this process, unless gender is considered.