For example, the polymorphisms of interleukin (IL) -10, IL-6 and tumor necrosis factor α (TNF-α) are related to a high risk of developing schizophrenia (Shivakumar et al., 2018; Xiu et al., 2018) and their levels in blood are higher in schizophrenia patients compared with healthy subjects (Kunz et al., 2011; Lee et al., 2017). Here, TNF is linked to schizophrenia.