Obsessive-compulsive disorder (OCD) is a severe psychiatric condition with a clear genetic component (Nicolini et al., 2009) in which neurodevelopmental mechanisms may be etiologically important. Brain-derived neurotrophic factor (BDNF) is an interesting candidate for molecular analysis in OCD on the basis of potential functional relevance, positive association studies, and reported interaction between this gene and other neurotransmitters implicated in this disorder.