Biology 202
1998 First Web Reports
On Serendip

Obsessive-Compulsive Disorder

Rachel Kaplan

Obsessive-Compulsive Disorder (OCD) is an anxiety disorder which can afflict a person throughout his lifetime: "The individual who suffers from OCD becomes trapped in a pattern of repetitive thoughts and behaviors that are senseless and distressing but extremely difficult to overcome" ( Obsessions and compulsions are the two main components of this disorder. The former are often highly negative such as an ever-present fear of germs. Compulsions such as repeated handwashings are rituals designed to lessen anxiety produced by obsessions. Depending on the severity, OCD can have an adverse affect on every realm of a person's life. The outlook is optimistic, however, because research has shown that even people suffering from severe OCD may benefit from medication, behavioral therapy, or a combination of the two.

Researchers have gained much insight into the cause of the disorder by comparing OCD brains with "normal" brains. There is continued debate about whether OCD is caused by neurobiological factors, environmental influences, or both. There is at least evidence to show that the brains of OCD sufferers differ from "normal" brains in systematic ways: "Recent preliminary studies of the brain using magnetic resonance imaging showed that the subjects with OCD had significantly less white matter than did normal control subjects, suggesting a widely distributed brain abnormality in OCD" ( The white matter, which lies beneath the cerebral cortex, contains axons which connect neurons in the cerebral cortex to neurons in other parts of the brain. Lowered white matter content seems to suggest that there is less intracranial communication in the brains of OCD patients. Another study showed that "persons having OCD often exhibit abnormal rates of metabolic activity [in direct correlation with the severity of the disorder] in the frontal lobe and the basal ganglia [more specifically in the orbital cortex] of the brain" ( It has been suggested that the orbital cortex is responsible for stimulating a "worry circuit" consisting of the "caudate nucleus, a part of the basal ganglia that helps in switching gears from one thought to another; the cingulate gyrus, which wrenches the gut with dread, and the thalamus, which processes the body's sensory inputs" ( It is hypothesized that in OCD, these 3 respective brain areas become linked in action. Susan Swedo and her colleagues at NIMH have hypothesized that because OCD behaviors have been connected with antibodies attacking the basal ganglia, repeated strep throat infections in childhood may lead the formation of the fused "worry circuit."

Other researchers have suggested that OCD results from "an imbalance of a chemical [(neurotransmitter)] in the brain called serotonin [(note: other NT's such as dopamine and norepinephrine have also been implicated in OCD)]" ( Studies have shown that OCD patients tend to have lower levels of this neurotransmitter (NT). Evidence which supports this hypothesis is the fact that drugs which increase serotonin output reduce symptoms of OCD. Because serotonin is essential for nerve cell communication, perhaps these lower levels of NT in OCD patients account for the fewer axons comprising their white matter. Medication and behavioral therapy are best when used in conjunction with one another. Both can actually produce a similar alteration of brain chemistry over time. Schwartz and Baxter of UCLA and the U. of Alabama have proposed that the 3 brain parts involved in the "worry circuit" can become unlinked with either Prozac or 10 weeks of behavioral therapy ( Evidence for the breakup of the "worry circuit" comes from PET scans which show less activity in the right caudate nucleus after effective pharmacological or psychological therapy.

The tricyclic antidepressant, Anafranil, and the selective serotonin reuptake inhibitors, Luvox and Prozac, have been proven to be especially effective at treating OCD ( These medicines may help produce a healthy balance of serotonin in the brain. Unfortunately, once the medication is discontinued the symptoms often reappear.

One very effective form of behavioral therapy involves teaching the patient "exposure and response prevention techniques": how to deal with obsessions and compulsions without rituals ( In order to confront a fear of germs a patient might be asked to touch a garbage can and then to refrain from washing his hands. The patient's anxiety would mount initially, but after a long enough period of time it would subside in a process known as extinction. If this process was performed continually over time, than the overall anxiety would decrease surrounding the obsession (habituation).

This behavioral treatment is simply a reconditioning technique which exemplifies the bi-directional nature of the brain; an incoming pattern of sensory information, i.e. unclean garbage can, is rerouted in the brain and processed in a different way because of the lack of a "handwashing output." This varied processing of information leads to an altered emotional state in the person. Habituation can be explained by the fact that over time, given that the brain is plastic, connections can become increasingly linked (see "worry circuit"). The reason the therapy works is because OCD sufferers can resist even the most intense urge to follow through on a compulsion. Aiming free-will in the right directions is the key to overcoming OCD. Schwartz explains that behavioral therapy is possible in humans because they can choose not to act every time on signals sent by the brain. In fact, "The more you don't listen, the less you are bothered by tyrannical obsessions" (

More than 2% of the U.S. population suffers from OCD, making it more prevalent than both schizophrenia and bipolar disorder. Fortunately, research has been able to provide increasing relief for patients. Studies on OCD have also been able to shed much light into the complex and often inscrutable workings of the brain.

WWW Sources

Obsessive-Compulsive Foundation, based in CT

All about Obsessive Compulsive Disorder from

Factsheets on Anxiety Disoders - Obsessive-Compulsive Disorder from Nat'l Mental Health Association

From Selective Serotonin Reuptake Inhibitors (SSRIs)
Obsessive-Compulsive Disorder has a Biological Foundation
How Medications Work
Medical Treatment

Serotonin Basics -- Part 1, Part 2, and Part 3, from Usenet

Searching for a Better Understanding of OCD by Anne Brown
Ask the Expert - OCD's Cause
The Many Different Faces of Obsessive-Compulsive Disorder by James Broatch, M.S.W.
Obsessive-Compulsive Disorder: A Treatable Disorder from National Anxiety Foundation
Obsessive-Compulsive Disorder, NIMH pamphlet

Obsessive-Compulsive Disorder (OCD) research at NIMH
Systematic Changes in Cerebral Glucose Metabolic Rate After Successful Behavior Modification Treatment of Obsessive-Compulsive Disorder. Online abstract at NIMH
Obsessive-Compulsive Disorder, NIMH publication

From Symptoms of OCD
Treating OCD
What Couses OCD?

| Forum | Back to Biology | Back to Serendip |

Send us your comments at Serendip
© by Serendip 1994- - Last Modified: (none)

This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.

Contribute Thoughts | Search Serendip for Other Papers | Serendip Home Page