IL1B and schizophrenia: Two meta-analyses illustrate that IL-6 is consistently elevated in serum and plasma of patients with schizophrenia,17, 18 whereas IL-1β and TNF-α were found to be increased in one meta-analysis,18 but not in the other.17 Genetic studies have also linked polymorphisms in major histocompatibility complex (MHC) regions with risk of schizophrenia.19, 20