There were no sociodemographic differences between the groups. The standard error of mean serum BDNF levels were reduced in unmedicated OCD patients (0.47+0.038) when compared to healthy controls (0.75+0.060) (P<.001). The patients with the presence of sex/religion obsessive-compulsive symptoms (OCS) dimension (P=.002), with chronic course of OCS (P=.022) and the presence of lifetime major depression (P=.016) and social anxiety (P=.030) presented higher levels of BDNF than OCD patients without those features. The severity of aggression (P=.039) and sex/religion (P<.001) OCS dimension presented direct (moderate and strong, respectively) correlation with serum BDNF levels in this sample. Serum BDNF levels were decreased in OCD patients when compared to healthy controls.Discussion/ConclusionSexual and religious content of symptoms and aggression and sex/religion dimensions severity should be better explored, since these specific OCS dimensions could be based on neurocircuits diverse from those of the other OCS dimensions.