There are no laboratory tests that can diagnose a person with depression. There are tests that can be used to rule it out, though. Because other medical conditions such as hypothyroidism and viral infections can produce symptoms similar to those of depression, your doctor may want to first consider whether you might be suffering from any of those illnesses.
The best way for a mental health professional to diagnose depression is with a thorough interview with the patient. In addition, your doctor may ask you to fill out the following depression rating questionnaires to help better gauge your symptoms.
Beck Depression Inventory
The Beck Depression Inventory (BDI) is made up of 21 (self-reported depression) questions designed to help mental health professionals assess the mood, symptoms, and behaviors of people who are depressed. Each answer is given a score of zero through three that indicates severity of symptoms.
Hamilton Depression Rating Scale
The Hamilton Depression Rating Scale (HDRS) is a questionnaire designed to help health care professionals determine the severity of depression in patients who have already been diagnosed with depression. It also consists of 21 questions; each relates to a particular sign or symptom of depression. Multiple-choice answers are given a score of zero through four. Higher total scores indicate more severe depression.
Zung Self-Rating Scale for Depression
This is a screening tool that patients who have been diagnosed with major depression can use to assess the level of their depression. It is a 20-question tool that provides a score range from 20 to 80. Most people with depression score between 50 and 69. A score above that indicates severe depression.
People who are depressed often seek help first from their primary care physicians. Patients might then be referred to a trained mental health professional.
Your doctor may perform a physical exam or blood work to rule out other conditions that could be contributing to your mood. Some medications and illnesses, such as a viral infection, thyroid disorder, or significant hormonal changes, can cause symptoms that are similar to depression.
If your doctor can find no other cause for the symptoms, he should perform a psychological evaluation or refer you to a licensed mental health expert.
To determine whether a person has depression, doctors look for specific symptoms known as diagnostic criteria. Expect your therapist or doctor to ask in-depth questions about your symptoms, mood, behavior, and day-to-day activities, as well as your family’s psychological history. You may also be asked to fill out a questionnaire that will help the doctor further evaluate your symptoms. Be prepared to tell how long you’ve been feeling depressed, what brought on the depression, and whether you’ve been depressed in the past.
To be diagnosed with major depressive disorder, a patient must display five of the following signs or symptoms and must have been experiencing them for at least two weeks:
- sadness or depression
- lack of interest or pleasure in almost all activities, especially those that used to be pleasurable
- trouble sleeping or sleeping all the time
- fatigue or lack of energy
- feelings of worthlessness and guilt
- an inability to concentrate or think
- change in appetite
- agitation or moving in slow motion
- recurrent thoughts of death
If you are suffering from clinical depression, your doctor will also evaluate you for the various types of depressive disorders, including seasonal affective disorder, postpartum depression, atypical depression, cyclothymia, dysthymia, and bipolar disorder.