Cambridge researchers have discovered that measuring activity in a
region of the brain could help to identify people at risk of developing
obsessive compulsive disorder (OCD).
As the current diagnosis
of OCD is based on a clinical interview and often does not occur until
the disorder has progressed, this could enable earlier more objective
detection, and intervention.
The scientists, funded by the
Medical Research Council and Wellcome Trust, have discovered that
people with OCD and their close family members show under-activation of
brain areas responsible for stopping habitual behaviour. This is the
first time that scientists have associated functional changes in the
brain with familial risk for the disorder. Their findings are reported
in the 18 July edition of Science.
Obsessive compulsive
disorder is a debilitating condition that affects 2-3% of the
population at some point in life. Patients suffer from recurrent
intrusive thoughts (obsessions) that are distressing and hard to
suppress. Examples include fears of contamination, or that something
terrible will happen to a loved one. They also suffer from repetitive
rituals (compulsions), which are often designed to neutralise these
thoughts. Examples include hand-washing and checking gas hobs. These
symptoms cause distress and can occupy hours during the day,
interfering with quality of life and the ability to work.
Although
OCD tends to run in families, genetic factors responsible for this
heritability are not known. Genes may pose a risk for OCD by
influencing how the brain develops.
Dr Samuel Chamberlain at
the University of Cambridge's Department of Psychiatry used functional
magnetic resonance imaging (fMRI) to measure brain activity in the
lateral orbitofrontal cortex (OFC). Located in the frontal lobes the
lateral OFC is involved in decision making and behaviour.
Volunteers
were asked to look at two pictures on a screen, each image had a house
and a face superimposed. The volunteers were asked to use trial and
error to work out whether the house or face was the correct target.
Volunteers pressed a button to indicate which image they believed to be
the target and feedback of 'correct' or 'incorrect' was given on the
screen. After the correct target had been identified six times in a row
it changed so the volunteer had to learn again. fMRI was used to
monitor their patterns of brain activity throughout.
Fourteen
volunteers without a family history of OCD, 14 people with OCD and 12
immediate relatives of these patients took the picture test. Later
comparison of fMRI images of their brain activity throughout showed
under-activation in the lateral orbitofrontal cortex and other brain
areas in both the OCD patients and their family members.
Dr
Chamberlain, who led the study, explains, "Impaired function in brain
areas controlling flexible behaviour probably predisposes people to
developing the compulsive rigid symptoms that are characteristic of
OCD. This study shows that these brain changes run in families and
represent a candidate vulnerability factor. The current diagnosis of
OCD is subjective and improved understanding of the underlying causes
of OCD could lead to more accurate diagnosis and improved clinical
treatments.
"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."
Source: EurekAlert (Press Release)
