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Treatment expectations are known to play an important role with regard to positive and negative effects of pharmacological and psychological interventions (Amanzio et al., 2009; Constantino et al., 2011; Rief et al., 2015; Schedlowski et al., 2015). Although research in this field is growing fast, some aspects remain unclear.
In pharmacological treatments it has not yet been examined whether prior experi-ence, representing one important mechanism responsible for treatment expectations, influences the occurrence of side effects. The first study of this thesis aimed at exam-ining whether an antidepressant’s side effects can be learned via classical condition-ing. Our results strongly suggest that learning plays an important role in the reoccur-rence of an antidepressant’s side effects.
The impact of treatment expectations on the intervention’s outcome is yet unclear for more recently developed psychological interventions, such as internet-based self-helps. In the second study, we examined whether treatment expectations influence the main outcome (tinnitus distress) in an internet-based self-help for patients suffer-ing from tinnitus. We found that pre-treatment expectations in the form of hope of improvement are a significant predictor for symptom improvement.
When it comes to negative effects of psychotherapy, so far the role of treatment ex-pectations has not been sufficiently examined and studies on incidence, origins, and types of negative effects are generally rare. Therefore, in a third study, we aimed at investigating what origins patients hold responsible for the occurrence of negative effects. In a qualitative interview study we were able to determine four main catego-ries to which the negative effects could be attributed: reasons for negative effects of an appropriate therapy, problems in the therapeutic relationship, reasons for negative effects due to unprofessionally performed therapy, and malpractice and unethical behavior. In the fourth study, we investigated whether the negative effects that are reported by the patients after psychotherapy are influenced by treatment expectations. Again, we found that expectations in the form of hope of improvement were a significant predictor for negative effects of psychotherapy in the direction that more hope of improvement led to less negative effects.
The studies conducted within this thesis underline the importance of treatment ex-pectations within pharmacological and psychological interventions and their influ-ence on positive and negative treatment outcomes.