High levels of the personality trait of neuroticism have been observed in
patients with anxiety disorders, suggesting that the trait and such disorders
might be related. In fact, the trait and generalized anxiety disorder could
well be due to the same genes.
This hypothesis comes from a study headed by John Hettema, M.D., Ph.D., an
assistant professor of psychiatry at Virginia Commonwealth University. A
report of the results is published in the September American Journal of
Generalized anxiety disorder is characterized by excessive, chronic worry
regarding multiple areas of life and includes symptoms such as irritability,
muscle tension, sleep disturbance, and difficulty concentrating.
To find out if generalized anxiety disorder and neuroticism are genetically
related, Hettema and his colleagues conducted a large twin study.
They studied about 8,000 identical and fraternal twins, including twins of
both genders. Subjects participated in either face-to-face or phone interviews
to find out whether they had had generalized anxiety disorder at some point in
their lives. The Structured Clinical Interview for DSM-III-R was used
for this purpose. They were also assessed for neuroticism with the short form
of the Eysenck Personality Questionnaire, which contains 12 items that overlap
with some of the diagnostic criteria for generalized anxiety disorder such as
irritability, nervousness, and excessive worrying.
The researchers then used the interview results to determine whether
subjects who scored high on the personality trait of neuroticism had also
experienced generalized anxiety disorder at some point in their lives. They
found that was the case in many subjects, suggesting that neuroticism and
generalized anxiety disorder might be genetically related.
They then looked to determine whether a coexistence of neuroticism and
generalized anxiety disorder occurred more often in identical than in
fraternal twins. They found that there was such a relationship, suggesting
that the same genes that cause neuroticism could cause generalized anxiety
disorder, since identical twins share 100 percent of their genes.
"Our results suggest that the genetic factors underlying neuroticism
are nearly indistinguishable from those that influence liability to
generalized anxiety disorder," Hettema and his colleagues concluded in
their study report.
One of the implications of their findings, they added, is that people with
high levels of neuroticism might be a useful starting point to hunt for genes
for generalized anxiety disorder.
As for the study's implications for current psychiatric practice,"
Although most psychiatrists do not routinely measure
neuroticism," Hettema told Psychiatric News, "if there
are indications of high neuroticism by whatever means, this would suggest that
screening for generalized anxiety disorder would be a good practice. However,
patients do not generally present with complaints of being neurotic, but
rather because they have actually developed a psychiatric syndrome like
generalized anxiety disorder, so the cat's already out of the bag."
The study was financed by the National Institute of Mental Health.
The study, "Genetic and Environmental Sources of Covariation
Between Generalized Anxiety Disorder and Neuroticism," is posted online
Am J Psychiatry20041611581