They evaluated CSF levels of total tau (t-Tau), phosphorylated tau (p-Tau), Aβ42, and neurofilament light chain protein (NfL) in patients with psychiatric diseases (depressive disorders, anxiety disorders, bipolar disorders, schizophrenia, and post-traumatic disorders) compared with patients with neurodegenerative disorders (probable AD, behavioural variant of frontotemporal dementia, Creutzfeldt–Jakob disease, Lewy Body disease, and probable progressive supranuclear palsy). Here, NEFL is linked to bipolar disorder.