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Understanding OCD - What Causes Obsessive Compulsive Disorder

written by: Dr. Kristie Leong • edited by: Paul Arnold • updated: 11/16/2010

OCD, or obsessive-compulsive disorder, is a disease shrouded in mystery. How much do we really know about the causes of OCD?

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    OCD, or obsessive-compulsive disorder, is a perplexing disease that causes an individual to have persistent intrusive thoughts and carry out repetitive, ritualistic behaviors as a way to relieve anxiety. Needless to say these repetitive behaviors, which include constant hand washing, cleaning or repeatedly "checking" things makes life difficult for its victims.

    The symptoms of OCD are varied, but the OCD sufferer feels powerless to stop their compulsions even though they know they’re irrational. Not surprisingly, many OCD sufferers experience anxiety and depression as a result of their illness. Unfortunately, researchers are only beginning to unlock the mysteries of this complex disease. What are the causes of OCD?

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    What Causes OCD? It’s Likely Multifactorial

    Researchers still don’t completely understand the cause of OCD, but it likely involves a genetic susceptibility to the disease combined with environmental influences. Some research shows that people with OCD have brain abnormalities such as too much or too little gray matter in certain areas of the brain. OCD is also more common in some families, and a person is more likely to have the disease if they have a close relative who also has it. It’s possible that OCD sufferers inherit structural brain changes that make them more susceptible to the disease.

    When researchers look for the causes of OCD, they’ve also focused on neurotransmitters. Neurotransmitters are brain chemicals that play a role in mood, movement and attention – among other functions. According to research, levels of two neurotransmitters, serotonin and dopamine, are often abnormal in people with OCD.

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    Serotonin Abnormalities: A Cause of OCD?

    The majority of research has centered on the role serotonin plays in the symptoms of OCD. Serotonin is a neurotransmitter associated with mood and sleep, and levels of serotonin are often low in people with depression. One theory is that receptors for serotonin in the brain may not be stimulated enough in people with OCD. Medications used to treat depression called serotonin-reuptake inhibitors, which increase the amount of serotonin in the brain often help the symptoms of OCD, lending further support to this theory.

    Even if OCD is due to structural brain changes or changes in neurotransmitter levels, the environment likely plays a role in how these symptoms are expressed. It is possible that environmental influences such as extreme stress could alter brain neurotransmitter levels in such a way as to cause OCD symptoms. It’s often difficult for researchers to separate out the role of genetics versus the environment in causing mental illnesses.

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    The Bottom Line?

    The causes of OCD are still not completely understood, but research suggests there may be a genetic susceptibility to the disease and that many OCD sufferers have abnormal levels of the neurotransmitters serotonin and dopamine. Hopefully, further studies will shed more light on the causes of this mysterious medical condition.

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    References

    BBC. "Causes of OCD".

    The Lancet 374 (9688): 491–9.

    Merck Manual. Eighteenth edition. 2006.