The following sections provide information on the various clinician-rated and self-report questionnaires and tests that you might be likely to encounter when being evaluated for depression.
Clinician Rating Scales
Hamilton Depression Rating Scale
The Hamilton Depression Rating Scale (HAM-D) is a 21-question multiple-choice questionnaire, used to rate the severity of a person's depression. It was originally published in 1960 by Max Hamilton, and is presently one of the most commonly used scales for rating depression in medical research. Based on an interview and observations, a clinician rates the severity of a person's depressive symptoms such as low mood, insomnia, agitation, anxiety and weight-loss on a graded scale. The first 17 questions of the HAM-D contribute to the total score and questions 18-21 are recorded to give further information about depression specifiers (e.g., whether paranoid symptoms are present). With the HAM-D, higher scores suggest more severe depression.
Beck Depression Inventory (BDI)
The BDI, created in 1961 by Dr. Aaron Beck (the same Dr. Beck who co-invented cognitive behavioral therapy), is a very commonly used tool for distinguishing between clinical depression and temporary unhappiness. This questionnaire is considered both reliable and valid when administered to adults. It is composed of statements concerning aspects of depression including hopelessness and irritability, cognitions (thoughts) such as guilt or feelings of being punished, and physical symptoms such as fatigue, weight loss, and lack of interest in sex. The BDI is a self-report instrument, so patients (rather than clinicians) answer the 21 multiple-choice items themselves. A total score of 0-9 indicates that a person is not significantly depressed, 10-18 indicates mild to moderate depression, 19-29 indicates moderate to severe depression and a score of 30-63 suggests that a person is severely depressed.
Zung Self-Rating Depression Scale
Similar to the BDI, the Zung Self-Rating Depression Scale is a short self-report survey used to quantify a person's level/severity of depressive symptoms. The Zung is composed of 20 items having to do with depression symptoms, and assesses mood (e.g., irritability), psychological symptoms (e.g., inability to concentrate), and somatic/body symptoms (e.g., fatigue). There are ten positively worded and ten negatively worded questions. Total scores range between 25 and 100. Scores of 25-49 indicate that a person is not depressed, 50-59 indicates mild depression, 60-69 suggests moderate depression, and a score of 70 and above suggests that someone is severely depressed. The use of the Zung has declined in the recent years due to some research suggesting that this scale is not very good at detecting symptom improvement after treatment has occurred.
Center for Epidemiologic Studies Depression Scale (CES-D)
The Center for Epidemiologic Studies Depression Scale (CES-D) is another common self-report screening test for measuring depression. The CES-D is composed of 20 questions about depressive feelings and behaviors occurring during the past week (e.g., feeling lonely, crying, feeling like a failure). Each question is scored on a scale of 1-3. On the CES-D, a person can score between zero and 60, with higher scores indicating more depressive symptoms.
Geriatric Depression Scale
The Geriatric Depression Scale (GDS) was designed specifically to identify depression in older adults. Many of the scales mentioned above were developed for use with younger or middle aged adults and are not appropriate for use with other groups of people. The GDS omits questions about common age-related physical symptoms so that older adults don't seem depressed when they actually aren't. In addition, the scale is less complicated than other scales, so it can be used with older adults who have mild to moderate problems with thinking and remembering (e.g., patients with Alzheimer's or Parkinson's disease).
The GDS is a relatively simple 30-question self-report assessment requiring "yes" or "no" answers, with one point assigned to each positive answer. A total score of 0-9 suggests that a person is not depressed, 10-19 suggests mild depression, and scores of 20-30 suggest that a person is severely depressed.
Depressive symptoms are sometimes measured with general questionnaires designed to assess several different types of mental disorders at once. For example, the General Health Questionnaire (GHQ) is used to detect short-term psychiatric disorders presenting with somatic (physical, body) symptoms, anxiety/insomnia, social dysfunction, or depressed mood. Making sense of scores from the GHQ requires comparing scores against norms (which are averaged results across many people, taking into account age, education level, gender, etc.). Cutoff points are used to indicate whether someone is experiencing a particular problem. These general types of scales are intended for screening purposes rather than for actual diagnosis. However, a score suggesting that depression is a concern will alert a clinician to follow-up with assessment necessary to determine a depression diagnosis.
As mentioned previously, there is no definitive diagnostic laboratory test that can establish whether someone has Major Depressive Disorder. For some time, researchers explored whether measurements of hormonal indicators could reliably distinguish between depressed and non-depressed individuals. The most prominent example of this sort of physical test was the dexamethasone suppression test, which measured cortisol levels and activation of the body's stress response system. Despite researchers' best efforts, the dexamethasone suppression test was never found to be a reliable indicator of Major Depression.
Even though lab tests cannot provide positive evidence for a diagnosis of MDD, such tests are very useful for ruling out medical causes of depression such as thyroid problems. A complete diagnostic work-up for depression should include tests for bacterial and viral infections, thyroid hormone levels, metabolic deficiencies, and autoimmune conditions (e.g., rheumatoid arthritis or lupus).