Psychiatric News July 15, 2005
Volume 40 Number 14
© 2005 American Psychiatric Association
p. 21
Psychiatric Illness May Affect Data on `Healthy' Subjects
Joan Arehart-Treichel
Some people who volunteer to be "healthy" controls in
psychiatric or other medical research may have personality disorders. Most
such volunteers, however, are not screened for Axis II disorders before the
study begins.
One of the hallmarks of medical research, including psychiatric studies, is
the use of "healthy control" subjects against which a population
of interest is compared.
Yet it looks as though a large number of persons who volunteer to serve as
control subjects have personality disorders, a new study suggests.
The study was conducted by Emil Coccaro, M.D., chair of psychiatry at the
University of Chicago, and colleagues. Results appear in the July Journal
of Psychiatric Research.
Some 340 individuals who answered a newspaper ad looking for people to
participate "in a medical research study of hormone response" and
to be paid for it were the focus of the study. Coccaro and his coworkers used
structured clinical interviews—the Structured Clinical Interview for
DSM Diagnoses and the Structured Interview for the Diagnosis of
DSM Personality Disorder (SIDP)—to determine whether any of the
volunteers currently had or had a history of any psychiatric disorders, and if
so, which ones.
They found that 45 percent of these volunteers had a lifetime history of
one or more Axis I disorders and that 48 percent of these volunteers had a
personality disorder.
Moreover, the most frequent personality disorder diagnosis was personality
disorder not otherwise specified (25 percent of those with a personality
disorder), followed by obsessive-compulsive disorder (7 percent), narcissistic
personality disorder (6 percent), and paranoid personality disorder (almost 6
percent).
Furthermore, volunteers with personality disorders were found to differ
from volunteers without such disorders in clinically significant ways. For
example, they tended to exhibit more impulsivity, affective lability, trait
anxiety, hostility, and aggression than the latter group did.
These findings have important implications, the researchers believe. For
example, with regard to Axis I disorders, the lifetime history of psychiatric
disorders found in these subjects is quite close to the 48 percent found in
studies of the general American population. Thus the subjects may well
represent the general population on this comparison. However, while 48 percent
of the subjects were found to have a personality disorder, only 15 percent of
the general American population meets criteria for such a diagnosis
(Psychiatric News, September 3, 2004).
And even if such individuals were a true random sample of Americans,
investigators would probably not want to use them as "healthy
controls" since there is reason to believe that some of the
characteristics they possess could bias study outcomes, Cocarro and his
coworkers indicated in their report. For instance, studies have shown that
trait anxiety can influence hypertension, and impulsiveness can alter
neurotransmitter activity.
The problem, Cocarro and his team concluded, is that while most scientists
screen potential control subjects for Axis I disorders (at least in
psychiatric research), they do not screen them for Axis II disorders. Hence
individuals with personality disorders can easily be enrolled to serve as
controls and thus may bias research outcomes.
"Two methodologic issues may compromise these data to some
extent," Paul Appelbaum, M.D., told Psychiatric News. In
addition to being chair of psychiatry at the University of Massachusetts and a
former APA president, Appelbaum has written extensively on the use of mentally
ill subjects in research studies.
"First, these subjects were recruited from a newspaper ad that began
by stressing the money that was being offered rather than, for example, the
opportunity to contribute to advancing knowledge of hormone responses....
Thus, the findings of a high prevalence of personality disorders in the
resulting group of volunteers may be specific to the means used here to
recruit them. Focus on a desire for money when you recruit subjects, and you
may get what you pay for. Second, the accuracy of the data is entirely
dependent on the validity of the diagnostic method used. Structured
instruments like the SIDP are known to overestimate—sometimes
markedly—the rate of personality disorders in a sample."
Yet assuming that the findings are valid, Appelbaum said, "they do
suggest reason for caution in recruiting and screening subjects.... The
authors suggest more intensive screening for personality disorders, but there
are other solutions too. It may well be worth experimenting with the
recruitment message, for example, stressing altruism versus self-interested
motives, to see the effect on who volunteers. Or more epidemiologically valid
methods of recruiting samples from the general population might be employed,
rather than relying on newspaper ads."
The study was funded by the National Institute of Mental Health.
An abstract of "High Prevalence of Personality Disorders Among
Healthy Volunteers for Research: Implications for Control-Group Bias"
can be accessed online at
<www.sciencedirect.com>
by clicking on "Browse A to Z of journals," then "J,"
then "The Journal of Psychiatric Research." 
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