Mothers, fathers, and full siblings of individuals with OCD and TD/CTD were each more likely to be affected with an AD, compared to unaffected individuals from the general population. In some analyses, particularly in TD/CTD, the risk was slightly higher among mothers than among fathers and siblings, but these differences were not statistically significant, as indicated by the overlapping confidence intervals. These findings confirm and extend previous studies that focused exclusively on mothers,17, 18 and suggest that, while maternal-specific factors cannot be fully ruled out, particularly in TD/CTD, such as the placental transmission of antibodies to the offspring – which may in turn activate the immune system in the child and alter normal brain development18 – genetic factors appear to be important. Given the increased attention to maternal immune activation in neuropsychiatric disorders,42, 43 future studies could examine if maternal infection and active AD during pregnancy are associated with increased risk of OCD and TD/CTD in their offspring and how this risk varies as a function of interaction with genetic and other environmental risk factors.
