At the time of this study, a key focus of research was exploring the genetics behind OCD and its comorbidities. Genetic association studies were conducted to look at how certain genes may be behind the expression of OCD and related disorders.
This study by Drs. Weissbecker and Nicolini aimed to investigate clinical and genetic differences between OCD patients with and without a tic disorder. They wanted to understand whether accounting for these differences — if they existed — would affect the results of prior genetic association studies between OCD and several candidate genes. By examining a dopamine receptor D4 gene (DRD4) polymorphism in 210 OCD patients (38 of whom had a comorbid tic disorder) and 202 healthy controls, the team found that allele 4R in the OCD patients was lower in frequency than the control group. However, there were no differences in alleles between the OCD with comorbid tic disorder group and the OCD without comorbid tic disorder group. The team could not exclude an association between the DRD4 gene and OCD, but more research is required.
*Camarena, B., Loyzaga, C., Aguilar, A., Weissbecker, K., & Nicolini, H. (2007). Association study between the dopamine receptor D4 gene and obsessive-compulsive disorder. European Neuropsychopharmacology, 17, 406-409. doi:10.1016/j.euroneuro.2006.08.001