Obsessive-compulsive disorder as a 5-HT subsystem-related behavioural disorder

A review of the research linking brain serotonin (also called 5-HT) function to obsessive-compulsive disorder (OCD) is presented. Clomipramine is an antidepressant drug that prevents the re-uptake of serotonin, with the result that more serotonin remains active. In the early 1980s, several studies found clomipramine to be more effective than other drugs of its type in reducing symptoms of OCD. Later studies found a relationship between improvement in OCD symptoms and reductions in concentrations of the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in cerebrospinal fluid (the fluid that bathes the brain and spinal cord). Reduced cerebrospinal levels of 5-HIAA imply a reduction in the re-uptake of serotonin. Studies evaluating the appropriate duration of treatment for OCD found that patients who improved after 5 to 27 months of clomipramine treatment, and were subsequently withdrawn from the drug, experienced a return of OCD symptoms within seven weeks. New, selective serotonin uptake inhibitors that have proven to be effective antidepressants (e.g., fluvoxamine) have also been tested and found to be highly effective in reducing OCD symptoms. Inducing serotonin activity by other means does not always improve OCD symptoms. For example, when OCD patients were administered m-chlorophenylpiperazine (m-CPP), which initiates serotonin activity, they became anxious and depressed, and their OCD symptoms increased. However, when m-CPP was administered to patients treated with clomipramine for several months, the depression, anxiety and OCD symptoms did not significantly increase. These paradoxical findings suggest that there may be a brain abnormality in OCD involving alterations and possible interactions of serotonin and related substances. (Consumer Summary produced by Reliance Medical Information, Inc.)