Nicotine crosses the placenta during pregnancy and can adversely affect foetal brain development. However, studies into the relationship between maternal smoking and schizophrenia, which can affect up to 1% of the population, have given conflicting results.
Researchers conducted a study involving 977 people born between 1983 and 1998 in Finland who were diagnosed with schizophrenia. They analysed the level of maternal serum cotinine, which is found in tobacco, from stored serum samples taken in the first two to four months of pregnancy.
After comparing the samples with matched controls, the researchers found that schizophrenia risk increased with cotinine levels. In offspring with the greatest cotinine exposure, the risk of schizophrenia was increased by 38% after adjusting for confounders.
Reporting in the American Journal of Psychiatry (online, 24 May 2016)
, the researchers say the results are the strongest evidence yet of a relationship between foetal nicotine exposure and schizophrenia.
 NiemelÃ¤ S, Sourander A, Surcel H-M et al. Prenatal nicotine exposure and risk of schizophrenia among offspring in a national birth cohort. American Journal of Psychiatry 2016. doi: 10.1176/appi.ajp.2016.15060800