Prenatal Tobacco Exposure and Schizophrenia

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In utero exposure to tobacco, in other words having a mother who smoked during pregnancy, has been associated with several developmental disorders including attention deficit disorder and learning problems. Research from the Finnish Prenatal Study of Schizophrenia, a nationwide cohort of people with schizophrenia, suggests a link between this illness and in utero tobacco exposure. Dr. Alan Brown of Columbia University in New York described 997 Finnish patients with schizophrenia matched with same-sex and same-age controls whose mothers had blood samples taken during pregnancy. The American and Finnish research team examined serum cotinine, a metabolite of nicotine and a reliable biomarker for tobacco use, in the banked blood samples.
 
Among the affected offspring, 20.2% were born to women with serum cotinine greater than 50 ng/ml, considered a sign of high tobacco use, compared with 14.7% of controls; the odds ratio was 1.38 (95% CI, 1.05-1.82, p = 0.02), with adjustment for maternal age, parental psychiatric disorder, and birth province. When serum cotinine was analyzed as a continuous variable, the effect was weaker, with a final odds ratio of 1.06 (CI, 1.004-1.12; p = 0.035) when adjusted for the same factors along with a measure of maternal inflammation, C-reactive protein (CRP), which was also determined in banked serum.
 
The findings, while far from conclusive, suggest a dose-response which is one sign of plausibility. Furthermore, nicotine crosses the placenta and is associated with neurodevelopmental effects including cortical thinning and changes in the P1 auditory evoked response. The physiologic mechanisms of smoking may include reduced placental perfusion, increased carbon monoxide, oxidative stress, and the direct effects of nicotine on nicotinic acetylcholine receptors, which are important regulators of other neurotransmitters, and of neuron migration and cell survival.
 
A. Brown, H. Surcel, S. Niemela, S. Hinkka-Yli-Salomäki, I. W. McKeague, A. Sourander. Epidemiological Evidence for Inflammation and Nicotine Exposure as Prenatal Risk Factors for Schizophrenia. Symposium 1-2, 15th International Congress on Schizophrenia Research, Colorado Springs, Colorado. March 29-April 1, 2015.