Neopterin levels and dexamethasone suppression test in obsessive–compulsive disorder

Neopterin, a biopterin precursor that is released by macrophages, is an important immunological marker in psychiatric disorders. It has been reported that glucocorticoids may cause suppression of cell-mediated immunity and consequently result in decreased neopterin levels. In the present study, we evaluated whether dexamethasone suppression test (DST) and neopterin findings were associated with pure obsessive–compulsive disorder (OCD) patients (OCD-D group) and the concomitant OCD and depression (OCD+D group). The sample comprised 44 patients with OCD (27 with OCD-D and 17 with OCD+D) and 30 control subjects. There was significantly higher DST nonsuppression in the OCD+D group than in the OCD-D group. With regard to mean neopterin levels, there was no significant difference between the OCD-D group and the control group, but there was a statistically significant difference between the OCD+D group and the control group. The OCD+D group had significantly lower neopterin levels than the 20 OCD-D group. We suggest that this distinction may reflect the fact that glucocorticoids can lead to suppression of cell-mediated immunity and consequently can result in decreased neopterin levels. In conclusion, our results suggest that not the OCD-D group had normal neopterin levels and DST results, and also that OCD may be a heterogeneous subtype characterized by some biological indicators or anxiety and affective disorders.