Underactive brain regions linked to obsessive-compulsive disorder
18 July 2008
Scientists at Cambridge University have identified underactive brain regions linked to the risk of developing obsessive-compulsive disorder (OCD), a debilitating condition that is thought to affect 2-3 per cent of the population at some point of life.
The identification of brain-based markers for people at increased risk of OCD could lead to more-accurate, earlier diagnosis and treatment of the disorder. Currently, diagnosis is made by clinical interview, usually once the disorder has progressed.
OCD tends to run in families but little is known about the genetic factors involved in the disease. The current research, published in the journal Science, is the first to link functional brain changes with the familial risk for OCD.
In the study, researchers tested 14 people without a history of OCD, 14 people with OCD, and 12 of the patients' immediate relatives, unaffected by the disorder. The volunteers were shown a series of pictures comprising a house and face superimposed and asked to use trial and error to identify which image was the 'correct' target. They were given feedback of 'correct' or 'incorrect' on the screen. When the correct target had been identified six times in a row the test changed.
Functional magnetic resonance imaging (which measures blood flow in the brain to highlight which areas are most active) was used to look at brain activity throughout the task.
The people with OCD and their close relatives showed underactivation in the lateral orbitofrontal cortex and other brain areas, compared with the brains of the people without a history of OCD. The lateral orbitofrontal cortex, which is found in the frontal lobes, is associated with decision making and behaviour.
"Impaired function in brain areas controlling flexible behaviour probably predisposes people to developing the compulsive rigid symptoms that are characteristic of OCD," says Dr Sam Chamberlain from Cambridge University, who led the study. "This study shows that these brain changes run in families and represent a candidate vulnerability factor.
"However, much work is still needed to identify the genes contributing to abnormal brain function in those at risk of OCD. We also need to investigate not only vulnerability factors, but also protective factors that account for why many people at genetic risk of the condition never go on to develop the symptoms."
Image: Functional magnetic resonance imaging scans of brains of healthy controls (left) and of people with obsessive-compulsive disorder (right); Adam Hampshire
References
Chamberlain SR et al. Orbitofrontal dysfunction in patients with obsessive-compulsive disorder and their unaffected relatives. Science 2008 [Epub ahead of print].