NRG1 and schizophrenia: Likewise, evidence of dysregulated gene expression of NRG1 (18–20), ErbB1/ErbB4 (21), and PI3K/AKT (22, 23) in peripheral tissues [i.e., whole blood, peripheral blood mononuclear cells (PBMCs), monocytes] in schizophrenia has also been shown in people with chronic schizophrenia.