There are no laboratory tests to diagnose depression. But there are tests that can be used to rule it out. Your doctor may perform blood work to check for 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 similar to depression.
If your doctor can find no other cause for your symptoms, they may refer you to a licensed mental health expert for evaluation.
Doctors look for specific symptoms to determine if a person has depression. Expect your therapist or doctor to ask in-depth questions about your mood, behavior, and day-to-day activities. You will also be asked about your family’s psychological history. You may also be asked to complete a depression-rating questionnaire. This can help gauge your level of depression.
Examples of such questionnaires include the following:
The Beck Depression Inventory (BDI) is made up of 21 self-reported depression questions. They are 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 to indicate severity of symptoms.
The Hamilton Depression Rating Scale (HDRS) is a questionnaire designed to help healthcare professionals determine the severity of depression in people who have already been diagnosed. 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.
The Zung Scale is a screening tool used to help assess the level of depression in people who are depressed. It is a 20-question test that provides a score range from 20 to 80. Most depressed people score between 50 and 69. A score above that indicates severe depression.
To be diagnosed with depression, someone must display five of the following symptoms for at least two weeks:
- sadness or depressed mood
- 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 focus
- change in appetite
- agitation or feelings of moving in slow motion
- recurring thoughts of death
There are many different types of depression that may be diagnosed. This includes:
- major depressive disorder
- major depressive disorder with seasonal patterns, previously known as seasonal affective disorder (SAD)
- postpartum depression
- atypical depression
Determining what type you have can help your doctor determine the best treatment for your specific needs.