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The New York Times
Tuesday 10 November 2009 Op-Ed Contributor The Short Life of a Diagnosis
By Simon Baron-Cohen
Cambridge, England -- THE Diagnostic and Statistical Manual of
Mental Disorders, published by the American Psychiatric Association, is the
bible of diagnosis in psychiatry, and is used not just by doctors around the
world but also by health insurers.
Changing any such central document is complicated. It should
therefore come as no surprise that a committee of experts charged with revising
the manual has caused consternation by considering removing Asperger syndrome
from the next edition, scheduled to appear in 2012. The committee argues that
the syndrome should be deleted because there is no clear separation between it
and its close neighbor, autism.
The experts propose that both conditions should be subsumed
under the term ?autism spectrum disorder,? with individuals differentiated by
levels of severity. It may be true that there is no hard and fast separation
between Asperger syndrome and classic autism, since they are currently
differentiated only by intelligence and onset of language. Both classic autism
and Asperger syndrome involve difficulties with social interaction and
communication, alongside unusually narrow interests and a strong desire for
repetition, but in Asperger syndrome, the person has good intelligence and
language acquisition.
The question of whether Asperger syndrome should be included
or excluded is the latest example of dramatic changes in history of the
diagnostic manual. The first manual, published in 1952, listed 106 ?mental
disorders.? The second (1968), listed 182, and famously removed homosexuality as
a disorder in a later printing. The third (1980) listed 265 disorders, taking
out ?neurosis.? The revised third version (1987) listed 292 disorders, while the
current fourth version cut the list of disorders back to 283.
This history reminds us that psychiatric diagnoses are not set
in stone. They are ?manmade,? and different generations of doctors sit around
the committee table and change how we think about ?mental
disorders.?
This in turn reminds us to set aside any assumption that the
diagnostic manual is a taxonomic system. Maybe one day it will achieve this
scientific value, but a classification system that can be changed so freely and
so frequently can?t be close to following Plato?s recommendation of ?carving
nature at its joints.?
Part of the reason the diagnostic manual can move the
boundaries and add or remove ?mental disorders? so easily is that it focuses on
surface appearances or behavior (symptoms) and is silent about causes. Symptoms
can be arranged into groups in many ways, and there is no single right way to
cluster them. Psychiatry is not at the stage of other branches of medicine,
where a diagnostic category depends on a known biological mechanism. An example
of where this does occur is Down syndrome, where surface appearances are
irrelevant. Instead the cause ? an extra copy of Chromosome 21 ? is the sole
determinant to obtain a diagnosis. Psychiatry, in contrast, does not yet have
any diagnostic blood tests with which to reveal a biological
mechanism.
So what should we do about Asperger syndrome? Although
originally described in German in 1944, the first article about it in English
was published in 1981, and Asperger syndrome made it only into the fourth
version of the manual, in 1994. That is, the international medical community
took 50 years to acknowledge it. In the last decade thousands of people have
been given the diagnosis. Seen through this historical lens, it seems a very
short time frame to be considering removing Asperger syndrome from the
manual.
We also need to be aware of the consequences of removing it.
First, what happens to those people and their families who waited so long for a
diagnostic label that does a good job of describing their profile? Will they
have to go back to the clinics to get their diagnoses changed? The likelihood of
causing them confusion and upset seems high.
Second, science hasn?t had a proper chance to test if there is
a biological difference between Asperger syndrome and classic autism. My
colleagues and I recently published the first candidate gene study of Asperger
syndrome, which identified 14 genes associated with the condition.
We don?t yet know if Asperger syndrome is genetically
identical or distinct from classic autism, but surely it makes scientific sense
to wait until these two subgroups have been thoroughly tested before lumping
them together in the diagnostic manual. I am the first to agree with the concept
of an autistic spectrum, but there may be important differences between
subgroups that the psychiatric association should not blur too
hastily.
Simon Baron-Cohen, the director of the Autism Research
Center at Cambridge University, is the author of ?The Essential
Difference.?
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