In this first part of a review on biological psychiatric aspects of obsessive-compulsive disorder (OCD), firstly a short introduction is given about historical, diagnostic and epidemiological issues concerning OCD. Subsequently pharmacologic treatment-studies are discussed. Only serotonin (5-HT) reuptake blockers are proven to be effective. There is accumulating evidence that this therapeutic effect is not due to antidepressant effects. The results of the treatment-studies strongly suggests that 5-HT is involved in OCD. CSF-studies seem to confirm this. Possibly the therapeutic effect is related with adaptive changes of 5-HT receptors. There is evidence that in a subgroup of O CD-patients the dopaminergic system is involved.
