Differentiating Neural Correlates of Anxiety and Depression in Healthy Individuals: an fMRI study

Abstract

Abstract This study investigated the relationship between neural activation patterns of anxiety and depression. A comprehensive neural model suggests three distinct neural biomarkers in anxiety disorders: reduced top-down control of dorsolateral prefrontal cortex (DLPFC) on the amygdala, amygdala hypersensitivity and an overactive Locus Coeruleus (LC). Comorbidity rates between anxiety disorders and depression are significant. Therefore, the same biomarkers should be expected in depression, but neural patterns for the LC seem to diverge. Based on literature of both disorders, it was predicted that depression severity could predict correspondence to the DLPFC and amygdala anxiety biomarkers, and a non-correspondence to the LC anxiety biomarker. To test the hypotheses, FMRI responses of the amygdala and DLPFC of the 117 participants were extracted and entered into a k-means analysis. The participants received estimates of correspondence to the three biomarkers. Depression was assessed with the DASS. Three regression analyses were conducted. The results do not suggest linear relationships between the biomarkers and depression, but rather curvilinear relationships. In the low depression range the hypotheses are accurate, but become counterintuitive when approaching clinical depression. A reason for the sudden curvilinear turn of the LC biomarker could be the way it was set-up, and high intra-biomarker correlations may induce a quadratic effect in the other two biomarkers. Alternative explanations include moderating variables, or insufficient power in the higher depression ranges. Future research would benefit from a more direct set-up of the LC biomarker, and a pre-screening for depression to reduce skewness in the sample.