There was no causal relationship between maternal smoking during pregnancy and subsequent schizophrenia or bipolar disorder in children, a large retrospective family-based study found.
Compared with children with no exposure to smoking during pregnancy, those with a high level of smoking exposure had an overall increased risk of severe mental illness (HR 1.51, 95% CI 1.44-1.59), reported Patrick D. Quinn, PhD, of Indiana University in Bloomington, and colleagues, writing online in JAMA Psychiatry.
However, this was only at the population level. When examining siblings where one was exposed to a high level of smoking and one was not, the researchers found that the associations weakened considerably and were non-significant (HR 1.14, 95% CI 0.96-1.35).