Biomedical Engineering Reference
In-Depth Information
complemented by studies of sleep architecture [62-64], eye movement abnormali-
ties [65, 66], and electrodermal and other measures of autonomic nervous system
activity [67]. Although these approaches have greatly expanded knowledge of the
neurobiology of psychiatric disorders by serving as research tools, they have found
no significant application to clinical practice or evidence-based practice guidelines
because the measures are not sufficiently associated with diagnosis or prognosis to
prove useful in clinical decision making [57, 68]. As biological measures
(“biomeasures” [68]) and new techniques are reported and considered for use as
clinically applicable biomarkers, it is important for researchers and clinicians both
to understand how these may or may not be ready for “prime time” and adoption
into widespread clinical use.
11.2.2
Potential for the Use of Biomarkers in the Clinical Care of Psychiatric
Patients
Biomarkers have great potential for improving care for psychiatric patients. Three
areas in particular can be identified: enhanced diagnostic accuracy, prognostic
information about the natural course of an individual's illness, and prediction of
response to treatment.
As described earlier, clinical signs and symptoms are the central basis for estab-
lishing psychiatric diagnoses [57]. Yet some symptoms may be present in multiple
diagnoses: A reduction in the amount of sleep can be a diagnostic element of a
depressive episode, a manic episode, or generalized anxiety disorder. Biomarkers
have promise for enhancing diagnostic accuracy in this arena. Consider, for exam-
ple, a 21-year-old patient with a 3-month bout of depression that has interfered with
college classwork and social relationships: Is this depression a component of unipo-
lar major depressive disorder (MDD), or does the person really suffer from bipolar
disorder (formerly called manic-depressive illness), but has not yet experienced a
clear manic episode, because the patient is early in the course of illness? In an older
patient with mild but measurable cognitive impairments, do these problems origi-
nate from the neurodegenerative changes of Alzheimer's disease (albeit mild in
severity at this point), from ischemic damage to white and gray matter structures as
is seen in vascular dementia, or from major depression (previously termed the
“pseudodementia” of depression)? In a child, are inattention and disruptive behav-
iors manifesting the symptoms of attention deficit hyperactivity disorder (ADHD),
the early onset of bipolar disorder, or are they simply reflective of coping skills that
are overwhelmed by stressful circumstances (e.g., parental divorce)? For most
patients, clinical information is sufficient to converge on the salient psychiatric diag-
nosis rapidly, but for many individuals, diagnostic ambiguity may challenge even
expert clinicians. The use of biological markers has potential to assist in this
important process, but more work is needed before the field will have useful tools
for this application.
Prognostic information is another area where biomarkers could offer valuable
insights. In oncology, the elevation of a tumor marker prompts an evaluation for a
recurrence of disease and initiation of treatment, even before clinical manifestations
would have led to a reevaluation. In contrast, for psychiatric disorders, an impend-
ing full relapse of a disorder (e.g., schizophrenia) is heralded principally by the
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