Objective: The authors analyzed archival dried blood spots obtained from newborns to assess whether levels of immunoglobulin G (IgG) directed at dietary antigens were associated with a later diagnosis of a nonaffective psychotic disorder.
Method: The study population consisted of individuals born in Sweden between 1975 and 1985 with verified register-based diagnoses of nonaffective psychoses made between 1987 and 2003 and comparison subjects matched on sex, date of birth, birth hospital, and municipality. A total of 211 case subjects and 553 comparison subjects consented to participate in the study. Data on factors associated with maternal status, pregnancy, and delivery were extracted from the Swedish Medical Birth Register. Levels of IgG directed at gliadin (a component of gluten) and casein (a milk protein) were analyzed in eluates from dried blood spots by enzyme-linked immunosorbent assay. Odds ratios were calculated for levels of IgG directed at gliadin or casein for nonaffective psychosis.
Results: Levels of anti-gliadin IgG (but not anti-casein IgG) above the 90th percentile of levels observed among comparison subjects were associated with nonaffective psychosis (odds ratio=1.7, 95% CI=1.1-2.8). This association was not confounded by differences in maternal age, immigrant status, or mode of delivery. Similarly, gestational age at birth, ponderal index, and birth weight were not related to maternal levels of anti-gliadin IgG.
Conclusions: High levels of anti-gliadin IgG in the maternal circulation are associated with an elevated risk for the development of a nonaffective psychosis in offspring. Research is needed to identify the mechanisms underlying this association in order to develop preventive strategies.