Fernandes Gomes et al. report the downregulation of CSF corticotropin-releasing hormone (CRH) in parkinsonian disorders, and associations with cognition, compared with cognitively unimpaired individuals and non-parkinsonian disorders like Alzheimer’s disease, all of which characterized by α-synuclein seed amplification assay. This evidence concerns the gene CRH and early-onset autosomal dominant Alzheimer disease.