As much as the phrase "OCD" has pervaded our daily conversations, obsessive-compulsive disorder is very much a clinically significant psychiatric condition. The disease is characterized by high levels of anxiety, repetitive thoughts, impulses and behavior that can at times severely impact the routine life of its sufferers. OCD is found in about 2.5 percent of the population and up to 3.1 percent in those with a college degree or higher.
Among the treatment options available for OCD, selective serotonin reuptake inhibitors (SSRIs), the same drugs commonly used to treat depression, are used the most widely. However, about 20 to 40 percent of all patients treated did not respond to the medications.
In order to investigate the reason behind failed pharmacotherapy treatments, researchers at the Hopkins School of Medicine's Department of Radiology and Radiological Science and the Kennedy Krieger Institute's Department of Behavioral Psychology used proton magnetic resonance imaging (MRI) to compare the difference in brain metabolism between OCD patients and healthy controls, and thereby identify the causes of the unsuccessful treatments.
The differences in brain metabolism among the subjects were compared by dividing the subjects into three groups: those who were well-treated with SSRI treatment (Rs), those who failed to respond to treatment (NR) and healthy controls.
Three factors were considered in analyzing the data obtained with spectroscopic imaging: the ratios of the neurological markers N?-acetylaspartate(NAA)/choline(Cho), NAA/creatine(Cr) and Cho/Cr.
N?-acetylaspartate is considered to be the best and most specific noninvasive neural marker and is valued for its reliability in diagnostic tests. Its levels are directly associated with the presence of neurological diseases or conditions. Changes in choline levels serve as indicators for pathological conditions, since an increased level of this compound is associated with brain tumor, demyelination and inflammation.
The thalamus and basal ganglia, in both the left and right hemispheres, were the regions selected for analysis due to previous research results, which indicated that pathological changes in OCD were evident in these regions of the brain.
Results showed that among the three groups of patients, the NRs showed significantly lower levels of NAA/CR in the right basal ganglia overall, indicating decreased neuronal density, neuronal atrophy and decreased mitochondrial NAA synthesis.
Increased levels of Cho have been found in patients with brain tumors, inflammation, demyelination (the degeneration of nerve cells) and gliosis (accumulation of non-neural cells in areas of neuron loss). The same has been found in patients in the NR group of this study.
These results show the reasons behind the lack of response in these patients to treatment, as OCD might have caused them to experience abnormalities in myelination or neural signal transduction.
The imaging showed that changes in NAA and Cho were limited to the right hemisphere, in concordance with previous studies on the effects of neurosurgery, suggesting that OCD affects the right hemisphere primarily.
The conclusions apply to the development of new treatments for OCD patients, especially ones who responded poorly to SSRIs. They will shed light on the causes of OCD and possibly other disorders.
