Everyone experiences intrusive, random and strange thoughts.  Most people are able to dismiss them from consciousness and move on.  But these random thoughts get “stuck” in the brains of individuals with OCD; they’re like the brain’s junk mail.  Most people have a spam filter and can simply ignore incoming junk mail.  But having OCD is like having a spam filter that has stopped working – the junk mail just keeps coming, and it won’t  stop.  Soon, the amount of junk mail exceeds the important mail, and the person with OCD becomes overwhelmed.  So why does the brain of individuals with OCD work this way? In other words, what causes OCD?

Using neuroimaging technologies in which pictures of the brain and its functioning are taken, researchers have been able to demonstrate that certain areas of the brain function differently in people with OCD compared with those who don’t.  Research findings suggest that OCD symptoms may involve communication errors among different parts of the brain, including the orbitofrontal cortex, the anterior cingulate cortex (both in the front of the brain), the striatum, and the thalamus (deeper parts of the brain).  Abnormalities in neurotransmitter systems – chemicals such serotonin, dopamine, glutamate (and possibly others) that send messages between brain cells – are also involved in the disorder.

Although it has been established that OCD has a neurobiological basis, research has been unable to point to any definitive cause or causes of OCD.  It is believed that OCD likely is the result of a combination of neurobiological, genetic, behavioral, cognitive, and environmental factors that trigger the disorder in a specific individual at a particular point in time.  Following is a discussion of how those factors may play a role in the onset of OCD.

A study funded by the National Institutes of Health examined DNA, and the results suggest that OCD and certain related psychiatric disorders may be associated with an uncommon mutation of the human serotonin transporter gene (hSERT).  People with severe OCD symptoms may have a second variation in the same gene.  Other research points to a possible genetic component, as well.  About 25% of OCD sufferers have an immediate family member with the disorder.  In addition, twin studies have indicated that if one twin has OCD, the other is more likely to have OCD when the twins are identical, rather than fraternal.  Overall, studies of twins with OCD estimate that genetics contributes approximately 45-65% of the risk for developing the disorder. 

A number of other factors may play a role in the onset of OCD, including behavioral, cognitive, and environmental factors.  Learning theorists, for example, suggest that behavioral conditioning may contribute to the development and maintenance of obsessions and compulsions.  More specifically, they believe that compulsions are actually learned responses that help an individual reduce or prevent anxiety or discomfort associated with obsessions or urges.  An individual who experiences an intrusive obsession regarding germs, for example, may engage in hand washing to reduce the anxiety triggered by the obsession.  Because this washing ritual temporarily reduces the anxiety, the probability that the individual will engage in hand washing when a contamination fear occurs in the future is increased.  As a result, compulsive behavior not only persists but actually becomes excessive.

Many cognitive theorists believe that individuals with OCD have faulty or dysfunctional beliefs, and that it is their misinterpretation of intrusive thoughts that leads to the creation of obsessions and compulsions.  According to the cognitive model of OCD, everyone experiences intrusive thoughts.  People with OCD, however, misinterpret these thoughts as being very important, personally significant, revealing about one’s character, or having catastrophic consequences.  The repeated misinterpretation of intrusive thoughts leads to the development of obsessions.  Because the obsessions are so distressing, the individual engages in compulsive behavior to try to resist, block, or neutralize them.

The Obsessive-Compulsive Cognitions Working Group, an international group of researchers who have proposed that the onset and maintenance of OCD are associated with maladaptive interpretations of cognitive intrusions, has identified six types of dysfunctional beliefs associated with OCD:

1.  Inflated responsibility: a belief that one has the ability to cause and/or is responsible for preventing negative outcomes;

2.  Overimportance of thoughts (also known as thought-action fusion): the belief that having a bad thought can influence the probability of the occurrence of a negative event or that having a bad thought (e.g., about doing something) is morally equivalent to actually doing it;

3.  Control of thoughts: A belief that it is both essential and possible to have total control over one’s own thoughts;

4.  Overestimation of threat: a belief that negative events are very probable and that they will be particularly bad;

5.  Perfectionism: a belief that one cannot make mistakes and that imperfection is unacceptable; and

6.  Intolerance for uncertainty: a belief that it is essential and possible to know, without a doubt, that negative events won’t happen.

Environmental factors may also contribute to the onset of OCD.  For example, traumatic brain injuries have been associated with the onset of OCD, which provides further evidence of a connection between brain function impairment and OCD.  And some children begin to exhibit sudden-onset OCD symptoms after a severe bacterial or viral infection such as strep throat or the flu.  Studies suggest the infection doesn’t actually cause OCD, but triggers symptoms in children who are genetically predisposed to the disorder.

Stress and parenting styles are environmental factors that have been blamed for causing OCD.  But no research has ever shown that stress or the way a person interacted with his or her parents during childhood causes OCD.  Stress can, however, be a factor in triggering OCD in someone who is predisposed to it, and OCD symptoms can worsen in times of severe stress.

In sum, although the definitive cause or causes of OCD have not yet been identified, research continually produces new evidence that hopefully will lead to more answers.  It is likely, however, that a delicate interplay between various risk factors over time is responsible for the onset and maintenance of OCD.

What doesn’t cause OCD

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