Maternal smoking seems to be more strongly associated with each disorder.
Systematic quantitative reviews were done and when appropriate the results were pooled in quantitative meta-analytic fashion. Wherever possible, information was extracted from each study relating to the odds ratios. Information was also sought on the extent to which the effects of parental smoking were altered by adjustment of potential confounding variables, and whether there was a dose-response relationship. The data on S.I.D.S. was based solely on case-control and cohort studies. These were an incredibly heterogenous group of studies reviewed for each of the above variables - although the authors did try to account for this using various statistical corrections.