Diagnostic Tests - Depression | Aetna InteliHealth

Although depression is often referred to as a "chemical imbalance," no single chemical causes depression. Rather, there are many chemicals involved in depression, and their interactions are very complex. Even for those chemicals that are known to play a role, such as serotonin, there is no useful way to measure their concentrations.

Diagnostic tests, however, can help evaluate people who are depressed. They can help identify any medical problems that may be causing depression or any negative health effects caused by depression. Diagnostic tests are part of the overall evaluation of this disorder.

Your health-care provider will decide which tests are right for you depending on your age, your physical symptoms and your health history. If you are younger than 40 and generally very healthy, few if any tests may be ordered. If you are older than 50 and have many symptoms, your health-care provider will probably have more tests in mind.

Remember, none of these tests are tests for depression itself. They may, however, indicate what may be causing your depression. The results of these tests can help determine the right treatment for you.

In an otherwise healthy person, health-care providers will often check the functioning of the thyroid gland by measuring the levels of certain hormones in the blood. Sometimes depression is the only symptom of low levels of thyroid hormone (or hypothyroidism).

If fatigue or weight loss is part of the picture, health-care providers may obtain a complete blood count and a chemistry profile.

A complete blood count (CBC) measures the number of red and white blood cells in your blood. Low numbers of red blood cells indicate anemia. And low or high numbers of white blood cells may show that you have an infection or some problem with your immune system.

A chemistry profile evaluates the function of your kidney and liver. It also uncovers irregularities in the concentration of various substances in your body (such as sugar and cholesterol).

Your health-care provider is not likely to order an X-ray unless he or she suspects a specific problem. For example, a chest X-ray is frequently done if there is a suspicion of some lung or heart disease. Other X-rays or scans may be part of an evaluation to rule out different kinds of cancer, although it is very uncommon for depression to be the first symptom of cancer.

Computed tomography (CT) and magnetic resonance imaging (MRI) may be used to evaluate neurological illnesses. Your health-care provider may suspect a neurological illness from the symptoms of your physical examination. An electroencephalogram may be used to diagnose a seizure disorder; it also provides other useful information about the brain's functioning.