Clinical Tests for Depression

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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