If you are planning
to see your doctor about depression, here is information about the kinds of
tests your doctor might ask for. First, keep in mind that not every test is a
"depression test." Some tests aren't used to diagnose clinical
depression but rather to rule out other serious medical conditions that may
cause similar symptoms.
In most cases, the
doctor will do a physical exam and ask for specific lab tests to make sure your
depression symptoms aren't related to a condition such as thyroid disease or
cancer. If your symptoms are related to another serious illness, treating that
illness may also help ease the depression.
Getting Ready for Medical Appointment
You're likely to start by seeing your primary care
doctor. However, in some cases when you call to set up an appointment, you may
be referred directly to a health provider who specializes in diagnosing and
treating mental health conditions (psychologist or psychiatrist).
Because appointments can be brief, and because
there's often a lot of ground to cover, it's a good idea to be well prepared
for your appointment. Here's some information to help you get ready for your
appointment, and know what to expect from your health provider:
- Write
down any symptoms you've had, including any
that may seem unrelated to the reason for which you scheduled the
appointment.
- Write
down key personal information, including any
major stresses or recent life changes.
- Make
a list of all medications, vitamins or
supplements that you're taking.
- Take
a family member or friend along, if possible.
Sometimes it can be difficult to remember all of the information provided
to you during an appointment. Someone who accompanies you may remember
something that you missed or forgot.
- Write down questions to ask your health provider.
Diagnosing
Depression and the Physical Exam
As mentioned
earlier, the main goal with a physical exam is usually to rule out a physical
cause for depression. When performing the physical exam, the doctor may focus
primarily on the nervous and hormonal systems. The doctor will try to identify
any major health concerns that may be contributing to symptoms of clinical
depression. For example, hypothyroidism -- caused by an underactive thyroid
gland -- is the most common medical condition associated with depressive
symptoms. Other hormone disorders associated with depression include
hyperthyroidism -- caused by an overactive thyroid -- and Cushing's disease --
a disorder of the adrenal gland.
Many central
nervous system illnesses and injuries can also lead to depression. For example,
depression might be associated with any of the following conditions:
- central nervous system tumors
- head trauma
- multiple sclerosis
- stroke
- syphilis
- various cancers (pancreas, prostate, breast)
Corticosteroid
medications such as prednisone, which people take for diseases such as
rheumatoid arthritis or asthma, are also associated with depression. Other
drugs, including illegal steroids and amphetamines and over-the-counter
appetite suppressants, may cause depression on withdrawal.
Diagnosing
Depression and Lab Tests
Your doctor can
usually tell if you have depression by asking you specific questions and doing
a physical exam. Your doctor may, however, ask for lab tests to rule out other
diagnoses. Your doctor will likely do blood tests to check for medical
conditions that may cause depressive symptoms. He or she will use the blood
tests to check for such things as anemia, and thyroid, hormone, and calcium
levels.
There are also
ongoing researches trying to develop reliable blood tests, which will be able
to identify depression in patients to confirm medical diagnoses.
Diagnosing
Depression and Other Testing Methods
The doctor may
include other standard tests as part of the initial physical exam. Among them
may be blood tests to check electrolytes, liver function, and kidney function.
Because the kidneys and liver are responsible for the elimination of depression
medications, impairment to either of these two organs may cause the drugs to
accumulate in the body.
Other tests may
include:
- CT scan or MRI of the brain to rule out serious
illnesses such as a brain tumor
- electrocardiogram (ECG), which is used to diagnose
some heart problems
- electroencephalogram (EEG), which uses an apparatus for recording electrical activity of the brain
"Static"
Brain Imaging
"Static" Imaging techniques can be used to
look for abnormalities only in brain structure. The most
widely used technique is computerized tomographic (CT) scanning. The
brain is X-rayed, and computerized techniques are used to reconstruct relatively
precise pictures of brain structures. CT does not provide a true diagnostic
laboratory test but it does provide a large amount of significant information
about pathological processes occurring in the brain. For example, venticular
enlargement is relatively common in schizophrenia, and this finding may confirm
the diagnosis of schizophrenia.
Another
imaging technique - nuclear magnetic response (NMR) scan - done by
nuclear magnetic resonance. Like CT, it is painless. As in the case of CT
scanning, computerized methods are used to reconstruct the obtained pictures.
It has two main advantages over CT scanning. First of all, it produces images
of extremely high resolution. Structures in the brain can be seen in incredibly
fine detail, with very clear differentiation between small gray and
white-matter structures. The second advantage is that NMR achieves these
pictures of living tissue at essentially no risk, Unlike CT scanning, which
uses a small amount of radiation, NMR uses none.
"Dynamic"
Brain Imaging
"Dynamic" brain imaging techniques permit
to actually observe how the brain works when it performs certain tasks. In
other words, it provides a way of measuring function rather than structure. The two commonest techniques for dynamic brain imaging are
studies of regional cerebral blood flow (RCBF) and positron-emission
tomographic (PET) scanning.
The technique of RCBF involves the use of
radioactive tracers, xenon-133, which are taken in brain tissue and can be used
to visualize which parts of the brain are most active. The labeled xenon emits
photons, which can be measured either by mapping flow on the surface of the
brain or with a computer-assisted tomotgraph much like that used in CT
scanning.
Patients suffering from particular kinds of mental
illness have greater or lesser blood flow in particular areas of the brain than
do normal people. For example, patients suffering from depression may have a
decreased metabolic rate in their brains, which may be either a cause or a
symptom of the disease. When the depression goes away with treatment, the
metabolic rate (as reflected by cerebral blood flow) goes up. Thus, one
application in this technique may be to monitor response to treatment.
PET
Scanning
PET
scanning is a technique that combines the best of both
worlds. It gives good resolution, much likes CT scanning, permitting the
clinician to see brain structures in relatively fine detail. Further, like
RCBF, it is a dynamic technique that permits the neuroscientist to watch the
brain at work and to observe which parts of it become more active in response
to various kinds of stimuli.
A brain imaging procedure involves the use of
positron-emitting substances that are injected into the body and taken up by
the brain. The radiation that they emit is measured and used to construct a
picture of the brain.
Pet scanning has a number of drawbacks. It is a very
expensive (positron-emitting isotopes are produced in a cyclotron), and it does
carry some risk (the injection of radioisotopes into a blood vessel). In the
future almost certainly positron-emitters will be attached to psychoactive
drugs or known neurotransmitter substances and their activities traced in the
brains of patients with mental illness, thereby helping us map areas of drug
action and of abnormalities in neurochemical transmission.
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