Maternal smoking during pregnancy and offspring attention-deficit/hyperactivity disorder: a case-control study in Japan.

Although maternal smoking during pregnancy has been shown to be associated with an increased risk of offspring attention-deficit/hyperactivity disorder (ADHD) in Western countries, there is no empirical evidence in non-Caucasian. Purpose of the present study is to examine the relationship between maternal smoking during pregnancy and offspring ADHD in Japanese population. A case-control study design was adopted. A total of 90 pairs of children with ADHD and mothers as well as 270 corresponding control pairs were recruited throughout the study period. A psychiatrist interviewed all the mothers of children with ADHD and control children and elicited information regarding their lifestyles during pregnancy, including active and passive smoking or drinking habits, as well as psychosocial and perinatal factors. Diagnosis of ADHD was made by each physician in charge according to DSM-IV diagnostic criteria. Logistic regression analysis was used to calculate odds ratios (OR) and 95% confidence intervals (CI) with adjustments for other possible confounding factors. Maternal active smoking during pregnancy was associated with an approximately twofold increased risk of offspring ADHD, even after adjusting for socioeconomic and perinatal confounding factors (OR 1.8 95% CI 0.9-3.6). However, the association was obviously attenuated when factors regarding parental psychopathological vulnerability were controlled (OR 1.3 95% CI 0.6-2.9). On the other hand, maternal passive smoking during pregnancy failed to show any material association with ADHD. These results suggested that a significant part of the association between maternal smoking during pregnancy, and ADHD might be explained by genetic factors including parental psychopathological vulnerability.