Neural temporal dynamics of stress in comorbid major depressive disorder and social anxiety disorder

Background: Despite advances in neurobiological research on Major Depressive Disorder and Social Anxiety Disorder, little is known about the neural functioning of individuals with comorbid depression/social anxiety. We examined the timing of neural responses to social stress in individuals with major depression and/or social anxiety. We hypothesized that having social anxiety would be associated with earlier responses to stress, having major depression would be associated with sustained responses to stress, and that comorbid participants would exhibit both of these response patterns. Methods: Participants were females diagnosed with pure depression (n = 12), pure social anxiety (n = 16), comorbid depression/social anxiety (n = 17), or as never having had any Axis-I disorder (control; n = 17). Blood oxygenation-level dependent activity (BOLD) was assessed with functional magnetic resonance imaging (fMRI). To induce social stress, participants prepared a speech that was ostensibly to be evaluated by a third party. Results: Whereas being diagnosed with depression was associated with a resurgence of activation in the medial frontal cortex late in the stressor, having social anxiety was associated with a vigilance-avoidance activation pattern in the occipital cortex and insula. Comorbid participants exhibited activation patterns that generally overlapped with the non-comorbid groups, with the exception of an intermediate level of activation, between the level of activation of the pure depression and social anxiety groups, in the middle and posterior cingulate cortex. Conclusions: These findings advance our understanding of the neural underpinnings of major depression and social anxiety, and of their comorbidity. Future research should elucidate more precisely the behavioral correlates of these patterns of brain activation.