Research has pointed to important psychopathological differences between persistent and episodic depressive disorders. Here, we tested the hypothesis that people with persistent rather than episodic depression have difficulty revising established expectations in response to novel positive information. In terms of underlying mechanisms, we predicted that these differences between the two subtypes would be related to the engagement in cognitive immunization (i.e. devaluing expectation-disconfirming positive information).

Prior to their psychotherapeutic treatment, 54 outpatients with persistent depressive disorder and 102 outpatients with episodic major depressive disorder completed an experimental task. In this task, participants watched other patients’ reports of positive effects of psychotherapy. Our primary outcome was change in treatment expectations from before to after watching the positive reports.

Overall, people with persistent depression had lower treatment expectations than people with episodic depression. In addition, they changed their treatment expectations less in response to other patients’ positive reports. This effect was greater for psychotherapy outcome expectations than for role expectations. The lack of expectation change in persistent depression relative to episodic depression was particularly pronounced in a cognitive immunization-promoting experimental condition.

The results indicate that people with persistent depression have difficulty adjusting their treatment expectations in response to positive information on psychotherapy. This may be a risk factor for poor treatment outcome. The results regarding cognitive immunization suggest that for people with persistent depression, slight doubts about the value of information on the positive effects of psychotherapy may be sufficient to prevent them from integrating this information.

Online treatments are increasing in number and are currently available for a wide range of clinical problems. To date little is known about the role of treatment expectations and other placebo-like mechanisms in online settings compared to traditional face-to-face treatment. To address this knowledge gap, we analyzed individual participant data from randomized clinical trials that compared online and face-to-face psychological interventions.

MEDLINE (Ovid) and PsycINFO (Ovid) were last searched on 2 February 2021. Randomized clinical trials of therapist guided online v. face-to-face psychological interventions for psychiatric or somatic conditions using a randomized controlled design were included. Titles, abstracts, and full texts of studies were independently screened by multiple observers. The Preferred Reporting Items for Systematic Reviews and Meta-analyses guideline was followed. Authors of the matching trials were contacted for individual participant data. Ratings from the Credibility and Expectancy Questionnaire and the primary outcome measure from each trial were used to estimate the association between expectation ratings and treatment outcomes in online v. face-to-face interventions, using a mixed-effects model.

Of 7045 screened studies, 62 full-text articles were retrieved whereof six studies fulfilled the criteria and provided individual participant data (n = 491). Overall, CEQ ratings predicted clinical outcomes (β = 0.27) at end of treatment with no moderating effect of treatment modality (online v. face-to-face).

Online treatment appears to be equally susceptible to expectancy effects as face-to-face therapy. This furthers our understanding of the importance of placebo-like factors in online treatment and may aid the improvement of healthcare in online settings.