We found high rates of complex phenotypes (i.e., TS+OCD or TS+OCD+ADHD), in both parents and offspring, and unexpectedly high rates of TS (with or without comorbidities) among mothers. The reasons for this are unclear. While we originally hypothesized that we would find evidence of bilineal mating in our sample, at least for ADHD, and that this might account for the high rates of ADHD in offspring, we did not find evidence for this. One possible explanation for the high rates of maternal TS and also perhaps for the high rates of complex phenotypes is that mothers with TS may be more likely to transmit TS and related phenotypes to their offspring than are TS-affected fathers. Examination of this hypothesis is outside the scope of the current analysis, requiring the inclusion of additional families, including bilineal families and those with offspring who are unaffected with TS.
