OC & Spectrum Disorders Research

Neurobiology of Obsessive-Compulsive Disorder

Imagine being unable to control your thoughts and feeling powerless until you perform specific acts or rituals. This is the situation people with obsessive-compulsive disorder (OCD) confront daily. According to Dr. Jeffrey Schwartz’s March/April 1997 Science & Medicine article, entitled "Obsessive-Compulsive Disorder," scientists have discovered new evidence that explains some causes of OCD. In short, OCD is an illness in which patients experience obsessions and then act on them by performing compulsions.

Obsessions occur when the brain generates repetitive, powerful thoughts that are intrusive and produce anxiety. In essence, patients cannot "move on," forget about or control their own thoughts. Compulsions are the physical actions or mental thoughts a patient carries out to reduce or eradicate the feelings associated with obsessive worrying (i.e., anxiety).

Examples of obsessions are feelings that a room is contaminated or that something bad will happen to someone. The obsessions lead to compulsions that cause a patient to repetitively wash a room from top to bottom until the room "felt clean" or perform rituals, such as praying, to ensure no one is harmed.

Although the patient realizes that these obsessions and compulsions are "unwanted, unreasonable and excessive," the person cannot stop listening to the thoughts and acting on them because of the pure feeling of dread the patient experiences until the compulsions are correctly performed. Surprisingly, OCD is more common than once suggested.

Today, one in forty people (2.5 percent of the population) have clinical OCD (where the symptoms are severe enough to interfere with daily functions) and approximately 10 percent of the population has sub-clinical OCD (where the thoughts are intrusive, but do not impair daily life and ability to function). Thus, almost 12.5 percent of the population experiences OCD symptoms at some point in their lives.

The primary question for scientists is how OCD manifests in the brain and what the biological basis of the disorder is. Typically, scientists divide OCD into two areas of study: how the repetition of thoughts occurs (i.e., the mechanism of OCD) and the content of OCD-related thoughts (e.g., worries about contamination or harm to others).

Through numerous studies, researchers have found that the mechanism of OCD is "neurologically mediated," such that it can be explained through scientific inquiry. In contrast, the content of OCD thoughts is best understood via conventional psychoanalysis, in which patients discuss their backgrounds, fears and beliefs with psychotherapists to resolve their problems.

To treat OCD, researchers focus on the biological/neurological basis of the disease, as the biology of OCD is the same for all patients, while the content of OCD thoughts varies considerably among patients.

Initially, researchers did not know what caused OCD and many psychiatrists believed it was purely a mental condition. However, studies of OCD and related disorders showed that OCD is caused by damage to a specific part of the brain called the basal ganglia. Thus, OCD is a biological disorder, rather than a "mental problem." Interestingly, researchers bolstered the notion that the basal ganglia causes OCD when they linked the onset of OCD symptoms to several events, including: bacterial infections, hypoxia (lack of oxygen to the brain) and neurotoxic agents.

A common element of these events is that they all damage portions of the basal ganglia. From these findings, scientists proposed that any damage to the basal ganglia might result in the onset of OCD symptoms. The significance of identifying the basal ganglia is that it shows that physical damage to a brain structure results in a neuropsychological (mental/emotional) condition.

Once OCD was localized to the basal ganglia, scientists delved deeper into the structure of the basal ganglia to understand what mechanisms cause OCD. From radiological studies, researchers learned that two brain structures that communicate with the basal ganglia are more active in patients with OCD. These two structures are known as the orbitofrontal cortex (OFC) and the anterior cingulate gyrus (ACG). Fortunately, it is only necessary to know that these structures act to detect errors in brain circuits and that their interactions with the basal ganglia explain how OCD manifests. Initially, two theories of basal ganglia-OFC/ACG interaction were proposed.

The first theory stated that damage to the OFC or ACG resulted in a loss of error-detection abilities, which caused the brain to increase repetition of messages and OCD to begin. However, a flaw of this theory is that it did not explain why patients report a feeling of dread and worry that something is wrong (i.e., that they have detected an error). The second theory postulated that OCD occurs as a result of the OFC and ACG being overstimulated.

When these structures are excited, they increase their abilities to detect errors; however, if they are stimulated beyond normal ranges (hyperexcited), they cannot accurately detect errors and may fire at inappropriate times. Thus, the OFC and ACG would send excessive, erroneous messages to the basal ganglia that there was a problem. This is exactly what patients report, a sense of "dread and an intractable feeling that ‘something is wrong’."

When the brain is in this repetitive, hyperexcited mode of generating and ruminating intrusive thoughts, it is in a state of "brain lock." Brain lock refers to four areas of the brain that are overstimulated in OCD patients; in essence, these four structures are "locked" together as one in patients with OCD. To release patients from "brain lock," physicians typically either prescribe medications (e.g., Prozac) or cognitive-behavioral therapy (CBT) or both. CBT is a technique that helps patients understand the inaccuracy of their OCD thoughts and learn new ways to respond to them, rather than performing compulsions.

An example of CBT for patients with contamination fears would be to make them sit in a "dirty" room for five minutes without washing or cleaning anything. After the patient begins to tolerate five minutes, the therapist will increase the exposure time or severity of the stimulus (e.g., a dirtier room) until the patient is able to tolerate the situation without feeling the need to clean. Based on previous findings, approximately 80 percent of OCD patients improve on medications, CBT or a combination of both. Surprisingly, most OCD patients can reduce OCD symptoms without medications.

These findings are significant because in either mechanism, medications or CBT, patients must change their brain chemistry and pathways to ameliorate OCD symptoms. The difference between these two approaches is simple: medications passively alter brain chemistry and decrease the intensity of OCD signals, while in CBT patients consciously alter their brain chemistry by changing their responses to obsessive thoughts. In this way, patients actively change their minds/thought processes to beat their OCD symptoms. Thus, it shows that mind over matter still may have some credence in the world and that a wonder drug may not be required to allow OCD patients to live happy, healthy lives.