Novel Approach to Mind Wandering in Major Depressive Disorder and Bipolar Disorder Patients: Does the Direction of Thoughts Matter?

Introduction: This study investigated the features of mind wandering in patients with major depressive disorder and bipolar disorder in comparison with the healthy control group. Method: The number and duration of internally- and externally-oriented thoughts during MW in 90 healthy control, major depressive disorder, and depressed bipolar disorder subjects were measured by a novel method of experience sampling experiment in the laboratory at the Royal Mental Health Centre of the University of Ottawa, Canada using the MATLAB software. Subjects also filled out BDI-II to evaluate current depressive symptoms. The methods used to analyze data included Chi-square, ANOVA, LSD Post Hoc Test, Pearson and Spearman correlation. Results: 1) an increased number of internally-oriented thought contents in MDD and BD; 2) the duration of time MDD and BD groups engage with the internal thoughts is almost twice the time the HC spend on it; 3) the relationship between the direction of thoughts during MW and depressive symptoms. Conclusion: Our results show depressed patients with MDD and BD spend a longer time on internal thoughts during MW which is related to the severity of their depressive symptoms, which carries clinical implications for both diagnosis and therapy.