Alterations of mental defeat and cognitive flexibility during cognitive behavioral therapy in patients with major depressive disorder: a single-arm pilot study

Objective Mental defeat affects the occurrence and chronicity of depression and cognitive flexibility. This study aimed to examine changes in mental defeat and cognitive flexibility scores after cognitive behavioral therapy including IR. In the intervention group, patients with depression (n = 18, mean age = 37.89 years) received 15 cognitive behavioral therapy sessions. Patients completed the Beck Depression Inventory-II; Mental Defeat Scale; Cognitive Flexibility Scale; EuroQol five dimensions questionnaire; Patient Health Questionnaire-9 and seven-item Generalized Anxiety Disorder Scale before the intervention, after six sessions, and post-intervention. The healthy control group (n = 33, mean age = 37.91) completed all scales once and did not receive treatment. Results Post-cognitive behavioral therapy, a significant decrease was observed in Beck Depression Inventory-II, Mental Defeat Scale, Cognitive Flexibility Scale, and Patient Health Questionnaire-9 scores. Although mental defeat and cognitive flexibility did not reach the level of the healthy control group, they demonstrated improvement. Therefore, when treating depression, mental defeat and cognitive flexibility should be measured in addition to depressive symptoms. Trial registration This study was registered retrospectively in the national UMIN Clinical Trials Registry on July 25, 2016 (registration ID: UMIN000023320)