Increased subcortical brain activity in anxious but not depressed individuals

AbstractObjective: Anxiety and depressive symptoms usually co-occur. Neuroimaging abnormalities in patients with depression and anxiety disorders are therefore related to a combination of symptoms. Here, we used a large population study to select individuals with only anxiety, only depressive, or combined anxiety and depressive symptoms to identify whether neuroimaging abnormalities are unique or shared between anxiety and depressive symptoms. Method: We selected four groups of 200 individuals (pure anxiety, pure depression, combined anxiety and depression, controls) from the UK Biobank, matched for age, sex, intelligence, and educational attainment (total N=800). We extracted the amplitude of low frequency fluctuations (ALFF) from resting-state functional magnetic resonance imaging data, which is an index of spontaneous neuronal activity. Group differences were assessed using permutation testing with age, sex and IQ as covariates. Results: Compared to controls, anxious individuals had higher ALFF values in many subcortical brain regions including the striatum, thalamus, medial temporal lobe, midbrain, pons, as well as the cerebellum and orbitofrontal gyrus (p<0.008, corrected). Anxious individuals also showed higher ALFF in the hippocampus, parahippocampal gyrus, cerebellum, and pons compared to pure depressive individuals (p<0.025, corrected). No significant differences were found for the depression and combined anxiety/depression groups. Conclusion: Anxiety but not depressive symptoms were associated with increased subcortical activity during rest. This suggest that anxiety symptoms may have the largest contribution to the neuroimaging abnormalities in patients with depression and anxiety disorders.