Neurobiological correlates of depressive symptoms in people with subjective and mild cognitive impairment

Objective To test the hypothesis that depressive symptoms correlate with Alzheimer's disease ( AD ) type changes in CSF and structural and functional imaging including hippocampus volume, cortical thickness, white matter lesions, Diffusion tensor imaging ( DTI ), and fluoro‐deoxy‐glucose positron emission tomography ( FDG ‐ PET ) in patient with subjective ( SCI ) and mild ( MCI ) cognitive impairment. Method In 60 patients, depressive symptoms were assessed using the Geriatric Depression Scale. The subjects underwent MRI , 18F‐ FDG PET imaging, and lumbar CSF extraction. Results Subjects with depressive symptoms ( n  = 24) did not have more pathological AD biomarkers than non‐depressed. Uncorrected there were trends towards larger hippocampal volumes ( P  = 0.06), less orbital WM damage measured by DTI ( P  = 0.10), and higher orbital glucose metabolism ( P  = 0.02) in the depressed group. The findings were similar when SCI and MCI were analyzed separately. Similarly, in patients with pathological CSF biomarkers (i.e., predementia AD , n  = 24), we found that correlations between scores on GDS and CSF Aß42 and P‐tau indicated less severe AD ‐specific CSF changes with increasing depression. Conclusion Depressive symptoms are common in SCI / MCI , but are not associated with pathological imaging or CSF biomarkers of AD . Depression can explain cognitive impairment in SCI / MCI or add to cognitive impairment leading to an earlier clinical investigation in predementia AD .