They discovered three key schizophrenia-specific alterations in the up-regulation of a 40-amino acid VGF-derived peptide, the down-regulation of transthyretin at 4 kDa, and a peptide cluster at 6,800-7,300 Da (which is likely to be influenced by the doubly charged ions of the transthyretin protein cluster) [6]. Here, TTR is linked to schizophrenia.