The validation of biomarkers allowing the discrimination of cognitive and behavioral disorders of psychiatric origin from those of neurodegenerative origin would facilitate diagnosis and improve patient management. Neurofilaments, which are markers of neuronal lysis, appear to be a promising biomarker. In a previous preliminary study, the investigators demonstrated significantly lower concentrations of neurofilaments in CSF of psychiatric patients compared to neurodegenerative diseases. The main objective of this study is to validate the plasma assay of neurofilament light chain as a biomarker for the differential diagnosis of psychiatric or neurodegenerative cognitive impairment. Other biomarkers of interest (Tau, TDP-43, GFAP and UCH-L1) will also be analyzed. A sub-part of this study will also focus on the retrospective analysis of the CSF/Plasma correlations of the different biomarkers mentioned above from tube bottom samples taken in routine care.