Cytokine concentrations throughout pregnancy and risk for psychosis in adult offspring: a longitudinal case-control study

Background Schizophrenia has been associated with pregnancy and birth complications and fetal exposure to inflammation is thought to be a common underlying mechanism. However, whether the risk is specific to particular phases of pregnancy is unclear. The aim of this study was to characterise and compare longitudinal patterns of maternal serum concentrations of cytokines across pregnancy between offspring who were later ascertained to have a psychotic disorder, non-psychotic siblings of these cases, and unrelated, non-psychotic individuals who served as controls. Methods The National Collaborative Perinatal Project was a large-scale prospective longitudinal study that assessed the effects of perinatal factors on infant and child development. At sites across the USA, over 50 000 pregnant women were enrolled during prenatal clinical visits between 1959 and 1965. The present study draws from the Philadelphia cohort, which includes 9236 surviving offspring of 6753 pregnant women. Psychotic disorder diagnoses in adulthood were assessed with review of medical records and were confirmed with a validation study. Concentrations of TNF alpha, IL-1 beta, IL-5, IL-6, IL-8, IL-10, and IL-17a were assessed using a multiplex bead assay in archived maternal serum samples collected across prenatal visits and birth. We characterized cytokine patterns with linear mixed models. Findings Our final sample comprised 90 cases, 79 siblings (of 40 cases), and 273 matched controls. Concentrations of proinflammatory cytokines TNF alpha, IL-1 beta, and IL-6 were significantly higher in maternal serum of offspring who later developed psychosis compared with maternal serum of matched controls. These differences were greatest in the first half of pregnancy (7-20 weeks), with no difference observed during the second half of pregnancy. Interpretation Our results suggest that exposure to high maternal proinflammatory cytokine concentrations in early pregnancy might play a part in psychosis. These findings place the timing of risk associated with maternal inflammation much earlier in prenatal development than previously documented in humans and provide insight into a potential developmental pathway to the disorder.