From Science Daily: A study published in the September 2016 issue of the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP) found an association between maternal smoking during pregnancy and an increased risk for Tourette syndrome and other chronic tic disorders. The link seems especially strong for complex presentations of Tourette syndrome in which two or more psychiatric disorders are present.
Smoking while pregnant has been associated with several behavioral manifestations in children, including neuropsychiatric difficulties such as chronic tic disorders and attention-deficit/hyperactivity disorder (ADHD). However, reasons for this association have not been fully elucidated. For example, mothers who smoke during pregnancy have a higher chance of having a psychiatric disorder, so it may be that the risk for psychiatric disorders is transferred from parent to child by genetic factors or environmental factors that are not directly related to smoking. Maternal smoking is also associated with prematurity and lower birth weight, which may, in turn, be a risk factor for subsequent behavioral problems in the child. Furthermore, parental smoking is associated with lower socioeconomic status and higher rates of alcohol and substance use, and these factors are also linked to behavioral changes in children.
Developing a clear understanding of both the risks for behavioral problems in children and then the mechanisms by which these risk factors operate is a complex undertaking that benefits from very large epidemiological samples and ongoing, rather than retrospective, data collection. These research methods use more reliable data and are less prone to bias.