UC San Diego

This dissertation consists of three studies which investigated environmental risk factors for autistic disorder. The first was a case-control study (861 cases, 123 controls identified February-April, 2005) which suggested that children with autistic disorder compared to those without were more likely to have been breastfed less than six months (OR 2.48, 95% CI 1.42, 4.35). Limiting the cases to children with regression in development found similar results (OR 1.95, 95% CI 1.01, 3.78). Children with autistic disorder were more likely to have used infant formula without docosahexaenoic acid and arachidonic acid supplementation than to have been exclusively breastfed (OR 4.41, 95% CI 1.24, 15.7), and the result appeared stronger after limiting cases to children with regression in development (OR 12.96, 95% CI 1.27, 132). Second, an ecological study showed significant positive associations between annual sales (1979-1985) of children's acetaminophen tablets and liquid and the number of autistic disorder cases in California who had the same birth years (p<0.05). Sales of children's aspirin products showed a significant negative association (p<0.01). Third, a case-control study (83 cases, 80 controls identified July 2005-January 2006) indicated that children with autistic disorder were more likely than those without autistic disorder to have used acetaminophen after measles -mumps-rubella vaccination when considering children 1 to 5 years of age (OR 6.11, 95% CI 1.42-26.3), children 1 to 18 years with regression in development (OR 3.97, 95% CI 1.11-14.3), and children 1 to 18 years with post- vaccination sequelae (OR 8.23, 95% CI 1.56-43.3), all adjusted for age, gender, mother's ethnicity, and the presence of illness concurrent with measles-mumps-rubella vaccination. Children with autistic disorder were more likely to have had illness concurrent with the measles- mumps-rubella vaccination when all cases were considered (OR 8.81, 95% CI 2.29-33.9) and after limiting cases to children with regression in development (OR 17.2, 95% CI 3.51-84.5), adjusting for age, gender, mother's ethnicity, and acetaminophen use after measles-mumps-rubella vaccination. These studies suggest that lack of breastfeeding, unsupplemented infant formula use, acetaminophen use, and illness concurrent with the measles -mumps-rubella vaccination may be risk factors for autistic disorder. Further investigation is required to confirm these preliminary findings