The Self in Depression and Anxiety as a Transdiagnostic and Differential-diagnostic Neural Marker: A Systematic Review.

Accurate and early diagnosis of Depression and Anxiety is met with the challenge of comorbid presentations and the neglect of the basic disturbances of self in current diagnostic criteria. Here, we review studies employing functional magnetic resonance imaging (fMRI) with self-based tasks in major depressive disorder (MDD) and anxiety disorders (AD) to determine the transdiagnostic and differential-diagnostic applicability of neural markers related to the self. This systematic review identified three main findings: (I) Large-scale brain-wide changes related to self-dysfunction overlap significantly between MDD and AD. (II) Regional changes are unspecific to tasks and stimuli confirming their specificity to the self as distinguished from other cognitive functions. (III) MDD affects regions related to emotional-cognitive processing like the anterior cingulate cortex, while AD involves prefrontal and insular regions associated with interoceptive and emotional-cognitive regulation. Our systematic review shows the utility of the self as a transdiagnostic marker that exhibits neural topographic similarities across the diagnostic boundaries of MDD and AD. More fine-grained regional differences between MDD and AD can be found within their underlying large scale neural similarities, allowing for their differential-diagnostic specification. In conclusion, we demonstrate the relevance of the self as both a transdiagnostic and differential diagnostic neural marker in MDD and AD.