Distinct Neural Correlates of Anxiety and Depression in Subjective Cognitive Decline versus Healthy Aging, a Microstructural Diffusion MRI Study.

Background: A common criticism of considering Subjective Cognitive Decline (SCD) as a preclinical stage of Alzheimer's Disease is that it may be explained by depression or anxiety1. We used NODDI, a diffusion microstructural model2, to explore the pathophysiology of depression and anxiety in SCD versus controls. Method: 325 participants in the Cam‐CAN study 3 (127 SCD) older than 55 were included in the analysis. Diffusion imaging data was collected on a 3T Siemens TIM Trio scanner with a 32‐channel head coil for 0, 1000 and 2000 s/mm2 b‐values and 30 gradient directions. Preprocessing and calculation of the NODDI metric Intracellular Volume Fraction (ICVF) were completed using MRTrix3, AMICO and MATLAB. The hippocampal cingulum bundle and fornix regions of interest (ROIs)4 were extracted from the ICBM‐DTI‐81 atlas. Depression and anxiety were assessed using the Hamilton Anxiety and Depression Scale (HADS). Linear regression models were completed in R. Gender and age were included as nuisance variables. Result: There were no differences in gender or age distribution between cohorts, however participants with SCD were more depressed and anxious on average (Table 1). There was a significant interaction effect between depression and cohort in the fornix (Figure 1), as well as between anxiety and cohort in the hippocampal cingulum (Figure 2). In post‐hoc analyses, only the SCD group showed a correlation between depression and ICVF in the fornix (Figure 1) while only controls showed a correlation between anxiety and ICVF in the hippocampal cingulum (Figure 2), indicating different pathophysiology underlying psychiatric symptoms in the two groups. Conclusion: Anxiety and depression appear to be associated with different microstructural features in SCD versus controls, suggesting anxiety and depression in SCD is a phenomenon distinct from anxiety and depression in healthy aging. Future work will explore the relationship between anxiety and depression and risk of conversion to mild cognitive impairment. 1. Mitchell AJ, Beaumont H, Ferguson D, et al. Acta Psychiatrica Scandinavica. 2014;130(6):439‐51. 2. Daducci A, Canales‐Rodriguez EJ, Zhang H, et al. Neuroimage. 2015;105:32‐44. 3. Shafto MA, Tyler LK, Dixon M, et al. BMC neurology. 2014;14(1):1‐25. 4. Kantarci K. Frontiers in Aging Neuroscience. 2014;6. [ABSTRACT FROM AUTHOR]