QUANTITATIVE ELECTROENCEPHALOGRAPHIC SUBTYPING OF OBSESSIVE-COMPULSIVE DISORDER

Current neuropsychological, electrophysiological, and other imaging da ta strongly suggest the existence of a neurobiological basis for obses sive-compulsive disorder (OCD), which was long considered to be exclus ively of psychogenic origin. The positive response of some OCD patient s to neurosurgery, as well as the efficacy of agents that selectively block serotonin reuptake, lends further support to a biological involv ement. However, a survey of the treatment literature reveals that only 45-62% of OCD patients improve with these specific medications. In a pilot study using a quantitative electroencephalographic (QEEG) method known as neurometrics, in which QEEG data from OCD patients were comp ared statistically with those from an age-appropriate normative popula tion, we previously reported the existence of two subtypes of OCD pati ents within a clinically homogeneous group of patients who met DSM-III -R criteria for OCD. Following pharmacological treatment, a clear rela tionship was found between treatment response and neurometric cluster membership. In this study, we have expanded the OCD population, adding patients from a second site, and have replicated the existence of two clusters of patients in an enlarged, statistically more robust popula tion. Cluster 1 was characterized by excess relative power in theta, e specially in the frontal and frontotemporal regions; cluster 2 was cha racterized by increased relative power in alpha. Further, 80.0% of the members of cluster 1 were found to be nonresponders to drug treatment , while 82.4% of the members of cluster 2 were found to be treatment r esponders. These findings suggest the existence of at least two pathop hysiological subgroups within the OCD population that share a common c linical expression, but show a differential response to treatment with serotonin reuptake inhibitors.