ANNALS OF CLINICAL PSYCHIATRY
GUEST EDITORIAL
ANNALS OF CLINICAL PSYCHIATRY 2016;28(3):153-154
The confusion of psychiatric comorbidity
Richard Balon, MD
Departments of Psychiatry and Behavioral
Neurosciences and Anesthesiology
Wayne State University School of Medicine
Detroit, Michigan, USA
CORRESPONDENCE
Richard Balon, MD
Departments of Psychiatry and
Behavioral Neurosciences and
Anesthesiology
Wayne State University School
of Medicine
Tolan Park Building
3901 Chrysler Service Drive
Detroit, MI 48201 USA
E-MAIL
[email protected]
AACP.com
F
or me, the concept of comorbidity as it has been applied in psychiatry always has been difficult to comprehend. Theoretically, a patient
could suffer from schizophrenia, persistent depressive disorder,
agoraphobia, Cannabis use disorder, mild neurocognitive disorder, and
perhaps a few more diagnostic entities. Yes, this example may be a bit of
an exaggeration, but is possible. We often see a similar host of psychiatric diagnoses in patients’ charts for a variety of reasons, such as a string
of treating psychiatrists who use or see different diagnoses or insurance
payment issues. However, I believe there are 3 main reasons in the present era that explain this phenomenon: lack of attention to careful descriptive psychopathology, lack of symptom and syndrome hierarchy, and the
inappropriate use of the term “comorbidity.” In a way, comorbidity is a
product of DSM-IV1 and DSM-52 because DSM-III3 kept a certain hierarchy of psychopathology.
The term comorbidity was introduced to medicine by Feinstein4 in
1970. As he wrote, “For the purpose of the discussion here, the term comorbidity will refer to any distinct additional entity that has existed or
that may occur during the clinical course of a patient who has the index
disease under the study.”4 He further expounded using toponymy: “The
toponymy of an event refers to its anatomic location and purported mechanism in relation to the index disease under scrutiny. A primary event is
attributable to the main pathological derangement of the index disease;
a secondary event arises from an auxiliary problem or complication.… In
relationship to such an index disease, a co-morbid disease can be regarded
as ancestral, supervening, or derivative. An ancestral disease is one that
caused, or was converted into, the index disease. Thus, an old pneumonia is often regarded as ancestral for a pulmonary ‘scar’ carcinoma, and
ulcerative colitis may sometimes be ancestral for carcinoma of the colon.
A supervening disease is caused by a new pathologic process that was predisposed by anatomic events of the index disease at the primary site. For
example, an acute pneumococcal pneumonia or lung abscess may super-
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ANNALS OF CLINICAL PSYCHIATRY
vene in cancer of the lung. A derivative disease is caused
by dissemination of the same pathologic process present
in the index disease. The dissemination may be produced
either by actual anatomic spread, or by systemic ‘secretion’ of hormones or toxins. Thus a cancer of the lung
may metastatically destroy the adrenal glands, producing
Addison’s disease; or the focal cancer may hormonally
create hypertrophic osteoarthropathy or the endocrinopathies of Cushing’s syndrome, hypercalcemia, or inappropriate secretion of vasopressin. A co-morbid disease
that has none of the dependent relations just described
may be regarded as independent, or unrelated to the
index disease.”4
As defined by Feinstein,4 comorbidity clearly does
not apply to psychiatry and should not be used in psychiatry. First, in the case I described at the beginning
of this editorial, we usually cannot ascertain ancestral,
REFERENCES
1. Diagnostic and statistical manual
disorders, 4th ed. Washington, DC,
Psychiatric Association; 1994.
2. Diagnostic and statistical manual
disorders, 5th ed. Washington, DC:
Psychiatric Association; 2013.
of mental
American
of mental
American
supervening, or derivative relationships between entities
such as schizophrenia and agoraphobia. We simply do
not know. We also cannot establish whether these are 2
or more distinct entities. We have started to address this
confusion by introducing new terminology in DSM-5, eg,
panic attack specifier,2 which allows us to avoid using a
“comorbid” coexisting diagnosis of panic disorder by
saying that there are panic attacks occurring during the
course of a specific other disorder, such as major depressive disorder. That brings back another issue—the hierarchy of psychopathology, symptoms, and syndromes—a
matter beyond the scope of this editorial.
More than a decade ago Maj5 suggested that
“Because ‘the use of imprecise language may lead to
correspondingly imprecise thinking,’ … this usage of the
term ‘comorbidity’ should probably be avoided.” He was
right. The question remains, “Why are we still using it?” ■
3. Diagnostic and statistical manual of mental
disorders, 3rd ed. Washington, DC: American
Psychiatric Association; 1980.
4. Feinstein AR. The pre-therapeutic classification
of co-morbidity in chronic disease. J Chronic Dis.
1970;23:455-468.
5. Maj M. “Psychiatric comorbidity”: an artefact
of current diagnostic systems? Br J Psychiatry.
2005;186:182-184.
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