Neural and Clinical Correlates of Cognitive Processes in Major Depressive Disorder and Posttraumatic Stress Disorder

Abstract

Major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) are chronic, debilitating illnesses. Impairments in cognitive processes such as social cognition, episodic simulation, and neuropsychological performance have been documented separately in both disorders. Despite our increasing knowledge of these impairments, the potential underlying transdiagnostic mechanisms remain relatively unexplored. This thesis examines correlates of these processes in persons with a primary diagnosis of MDD with a history of trauma exposure, and in persons with PTSD. The first study examined the association between the social cognitive domain of empathy and parental bonding in women with PTSD associated with childhood abuse. Participants with PTSD reported altered levels of cognitive and affective empathy, compared to controls. Paternal care during childhood was the only predictor of cognitive empathy (i.e., perspective taking). The second study investigated the specificity of episodic simulation of future positive, negative, and neutral events in relation to parental bonding and neuropsychological functioning among participants with MDD. Optimal parental bonding and higher scores on measures of neuropsychological functioning were associated with increased specificity of episodic simulation. In the third study, we examined the relation between dissociative symptoms and neuropsychological functioning in participants with MDD. Patients with MDD report significantly higher levels of dissociation as compared to controls, and more severe dissociation was related to poorer neuropsychological performance among this patient group. Lastly, using independent component analysis of resting-state fMRI data, the fourth study examined the association between intrinsic connectivity networks and neuropsychological performance among participants with MDD. Connectivity within the default mode, salience, and central executive networks was associated with neuropsychological and clinical (i.e., depression, dissociation, PTSD) variables. Overall, this thesis demonstrates that variables such as parental attachment, dissociation, and intrinsic connectivity networks may underlie some of the alterations in cognitive processes seen in MDD and trauma-related disorders.