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.

What does the doctor look for in the physical exam that helps to diagnose depression?

When performing the physical examination, 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.

What lab tests will my doctor do while checking for depression?

Your doctor can usually tell if you have depression by doing a physical exam and asking you specific questions. 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, thyroid and hormone levels, and calcium levels.

Are there other lab tests the doctor will want before diagnosing depression?

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 an arrhythmia, particularly heart block
electroencephalogram (EEG), which uses an apparatus for recording electrical activity from the brain