A study comparing individuals with persistent depressive disorder to those with episodic major depressive disorder found that those with persistent depression had lower treatment expectations. These individuals also changed their expectations about treatment outcomes less in response to positive reports by other patients. The research was published in Psychological Medicine.
Depression, or major depressive disorder, is a mood disorder characterized by persistent sadness or loss of interest lasting at least two weeks and causing significant impairment in daily functioning. It involves cognitive, emotional, and physical symptoms such as hopelessness, fatigue, sleep disturbances, appetite changes, and difficulty concentrating. Treatment typically involves psychotherapy, pharmacotherapy such as antidepressants, or a combination of both.
However, for many individuals who develop depression, treatment does not result in a remission of symptoms. Furthermore, a substantial share of individuals whose depressive symptoms do go into remission after treatment soon experience a new depressive episode. Overall, in around 20-30% of people who suffer from major depressive disorder, depressive symptoms become chronic, meaning that they persist for at least 2 years. Their condition may then be classified as “persistent depressive disorder” (PDD), as opposed to episodic depression characterized by a depressive episode followed by a remission of symptoms.
Study author Tobias Kube and his colleagues wanted to test two hypotheses. The first was that people with persistent depression adjust their expectations of psychotherapeutic treatment less than people with episodic depression in response to positive information. The second hypothesis was that people with persistent depression alter expectations of future life events less than people with episodic depression.
This study was part of a larger project that examined the role of cognitive immunization in expectation change in depression. Cognitive immunization is a psychological process in which individuals reinterpret or dismiss disconfirming evidence in order to preserve an existing belief or self-schema, thereby preventing belief change despite contradictory information.
Study participants were 156 individuals with major depressive disorder or persistent depressive disorder, recruited from a German university outpatient clinic and several private psychotherapy practices. They received 15 EUR for their participation. Of these individuals, 65.4% met the criteria for episodic major depression, while the remaining 34.6% met the criteria for persistent depressive disorder. Participants’ average age was approximately 35 years, and 67% of them were women.
At the beginning of the study procedure, participants reported their expectations of psychotherapeutic treatments (using the Milwaukee Psychotherapy Expectation Questionnaire) as well as their expectations of future life events (the Future Event Questionnaire). Next, they watched videos of four patients (played by amateur actors). These characters first reported on their symptoms, but then reported on how psychotherapy helped them overcome their problems.
Participants were randomly assigned to one of four experimental conditions that differed in the instructions they received for watching the videos. One group was told to focus on the similarities between themselves and the person in the video. Study authors hypothesized that this would make it difficult for these participants to disregard positive information about psychotherapy voiced by persons in the videos.
Another group was told to focus on the differences between themselves and the people in the video, hopefully making it easier for patients to engage in cognitive immunization and disregard the experiences of the person in the video. The third group was told to focus on the physical appearance of the people in the videos (a control condition). Finally, the fourth group did not receive any instructions before watching the videos.
After watching the videos, participants completed assessments of expectations of psychotherapeutic treatments and future life events again. They also completed an assessment of cognitive immunization (the Cognitive Immunization Against Other People’s Experiences scale), a 7-item assessment examining whether they interpreted the videos negatively, and a brief assessment of recall of video contents. Participants’ depressive symptoms were assessed using the Beck’s Depression Inventory – II.
Results showed that participants with persistent depression had, at the start, less positive expectations about the outcome of psychotherapy than people with episodic depression. After watching the videos, participants with persistent depression adjusted their expectations of psychotherapy much less than people with episodic depression. This difference was particularly pronounced in the group that was given instructions meant to promote cognitive immunization (focusing on differences).
However, contrary to the second hypothesis, the two groups did not differ in how they changed their expectations regarding future life events. Additionally, participants with episodic and persistent depression did not differ in their average level of cognitive immunization scores.
“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,” study authors concluded.
The study contributes to the scientific understanding of cognitive functioning specificities of individuals with depression. However, the study did not include a healthy control group. Therefore, it remains unknown whether and how much the observed effects are specific for depression and dissimilar to what would be observable in healthy individuals as well.
The paper, “Differences between persistent and episodic depression in processing novel positive information,” was authored by Tobias Kube, Edith Rapo, Mimi Houben, Thomas Gärtner, Eva-Lotta Brakemeier, Julia Anna Glombiewski, and Winfried Rief.