NEFL and Cognitive impairment: There is growing evidence that primary psychiatric disorders, in general, and psychotic disorders, in particular, are not characterized by increased levels of NfL in the cerebrospinal fluid (18, 20) or blood (16–18), not even in patients with treatment-resistant schizophrenia (21), a group with profound cognitive deficits (32) and possibly the group of schizophrenia patients with most neuronal damage (33).