Persistent Depressive Disorder

The purpose of this study is to compare the Cognitive Behavioral Analysis System of Psychotherapy (CBASP) conducted over 16 weeks (acute and continuation treatment) with Behavioral Activation (BA; same dose and duration) in persistently depressed treatment-resistant inpatients regarding efficacy, moderators and mediators of change.

Depression currently affects close to 2 million Canadians and is the leading cause of disability worldwide. Pharmacological treatments (antidepressant medication) and psychological treatments such as cognitive-behavioural therapy are available for depression, but the majority of those who receive treatment have an unsatisfactory response. On average, the combination of pharmacological and psychological treatment achieves better results than either treatment alone. However, the apparently superior results of combination treatment may be due to the fact that different individuals preferentially respond to pharmacological or psychological treatment. The invesitagtors have discovered several clinical factors and biomarkers that predict poor response to commonly used antidepressant medication: history of childhood maltreatment, loss of interest and reduced activity, a biomarker of systemic inflammation, and a genetic marker of sensitivity to environment. Indirect evidence suggests that the same factors may indicate the need for psychological treatment, but their usefulness as differential predictors of psychological and pharmacological treatment outcomes remains to be established. The investigators will test the hypothesis that a pre-determined clinical variables (history of childhood maltreatment, loss of interest and reduced activity) and biomarkers (serum C-reactive protein, a marker of systemic inflammation, and insulin resistence, an indicator of metabolic health) differentially predict response to antidepressants and to cognitive-behavioural psychotherapy with clinically significant accuracy. If this hypothesis is supported, the resulting predictor will allow personalized selection of treatment for depression, leading to improved outcomes and healthcare efficiency. Additional objectives include replication of additional predictors and integrative analyses aimed at refining the treatment choice algorithms.

This two-armed randomized controlled trial aims to investigate the effectiveness of an emotion regulation intervention in individuals with and without depressive disorders. The study encompasses participants diagnosed with mild to moderate major depression or persistent depressive disorder and healthy controls without a current depressive disorder. Participants will be randomly assigned to either the intervention group, receiving a valence-specific emotion regulation intervention in daily life, or a monitoring-only control group. The valence-specific intervention supports the implementation of different emotion regulation strategies based on whether a person is experiencing mainly positive or negative emotions. In contrast, participants in the control group will solely monitor their positive and negative emotions and the strategies used to regulate them. Outcome measures include emotion regulation ability, self-efficacy, and strategy use, depressive symptoms, positive and negative affect, and emotion beliefs (controllability, usefulness). A second aim of the study is to compare beliefs about positive emotions and strategies to regulate them between individuals with and without current depressive disorders. Furthermore, the investigators aim to examine why individuals might choose unfavorable emotion regulation strategies even when feeling good. Therefore, another research question is, how emotion beliefs might explain emotion regulation strategy choice.