The neural correlates of perinatal OCD: An exploratory investigation into serotonin risk genes and cortical morphology

Abstract

Introduction: Obsessive-compulsive disorder (OCD) is a complex disorder that is associated with significantly impaired functioning. The current prevailing model of OCD implicates dysfunction of the serotonergic neurotransmitter system and fronto-striatal neural networks, but challenges in replicating findings within OCD samples are often attributed to clinical heterogeneity. OCD symptoms that develop or worsen within the perinatal period appears to reflect a distinct subtype of the disorder, but the genetic and neurobiological factors that contributes to its presentation in women is poorly understood. In this dissertation, we aimed to review the literature on the genetic architecture of OCD, identify potential gene candidates for perinatal OCD and analyze one serotonin system gene according to OCD and possible subtypes using meta-analytic techniques. Based on these findings, we then tested the association of serotonergic candidate gene polymorphisms with the presence of infant-related obsessive-compulsive symptoms (OCS). Lastly, we investigated the cortical morphological features associated with perinatal OCD and OCS symptom severity in postpartum mothers. Results: From prior reports in the literature and our own meta-analytic investigation, polymorphic variants in genes coding for the serotonergic transporter and serotonin 2A receptor subtype (SLC6A4 and HTR2A, respectively) appear to be candidates for perinatal OCD due to their association in female samples. However, upon investigation in our perinatal sample (n=107), we found no evidence to support the association of the 5-HTTLPR polymorphism of SLC6A4 with perinatal-related OCS, but larger samples are needed to confirm this finding. Due to technical challenges, the HTR2A polymorphism remains to be tested. Our novel whole-brain explorations revealed distinct cortical morphology associated with symptom worsening across the perinatal period, irrespective of diagnosis. Cortical parameters were not able to differentiate mothers with and without OCD; however, OCD mothers displayed positive correlations between cortical surface area and symptom severity in widespread regions, including the frontal, parietal, temporal and occipital cortex. Conclusions: Overall, this body of work aimed to fill the gap in the literature by exploring the possible genetic and cortical correlates of perinatal-related OCS and OCD. While 5-HTTLPR or HTR2A are candidates for perinatal OCD, it is not yet clear whether they increase susceptibility for the development of infant-related OCS in the perinatal period. Distinct cortical alterations in surface area appeared alongside OCS exacerbation in the postpartum period in regions that extend beyond the frontoparietal network. This suggests that additional neural networks may be contributing to symptom severity and that the cortical plasticity that occurs across the perinatal period may predispose women for risk of OCD. Future studies should continue to use a multiple perspective approach, that utilizes genetic and neurobiological techniques, in order to provide greater insight into the etiology of perinatal OCD.