Khandaker GM, et al. - The association of childhood infection with IQ and adult nonaffective psychosis (NAP) was investigated to ascertain if shared familial confounding explains the infection-NAP and IQ-NAP associations, and to examine if IQ mediates and/or moderates the childhood infection-NAP association. Researchers observed that for the effects of infection on IQ and NAP, early childhood is a sensitive period. The associations of adult NAP with early-childhood infection and adolescent IQ were not fully explained by shared familial factors and may be causal. Individuals with psychosis showed lower premorbid IQ arising from unique environmental factors, such as early-childhood infection. Early-childhood infections by affecting neurodevelopment and by exaggerating the association of cognitive vulnerability with psychosis could increase the risk of NAP.