Zung SDS: Self-Rating Depression Scale
20-item classic depression scale. SDS Index 25–100; ≥50 indicates depression. Covers affective, somatic, psychomotor, and psychological symptoms. Public domain. Zung (1965).
Zung SDS Score Interpreter
SDS Index 50–59 corresponds to mild to moderate depressive symptoms.
20 items rated 1–4; 10 items reverse-scored. Raw total (20–80) converted to SDS Index = (raw ÷ 80) × 100. Higher Index = more depressive symptoms.
| SDS Index | Interpretation |
|---|---|
| 70+ | Severe depressionSDS Index ≥70 corresponds to severe depressive symptoms. |
| 60–69 | Moderate depressionSDS Index 60–69 corresponds to moderate to marked depressive symptoms. |
| 50–59 | Mild depressionSDS Index 50–59 corresponds to mild to moderate depressive symptoms. |
| 25–49 | Normal rangeSDS Index below 50 indicates minimal or no clinically significant depressive symptoms. |
Zung WW (1965). SDS Index severity ranges per Zung's conventional cutoffs — a commonly used clinical convention. Educational reference only — not a diagnostic tool.
The Zung SDS is a 20-item validated self-report measure of depression covering affective, somatic, psychomotor, and psychological symptoms. Scores expressed as an SDS Index (25–100). One of the most widely used depression scales in clinical research since 1965.
What is the Zung Self-Rating Depression Scale?
The Zung Self-Rating Depression Scale (SDS) was developed by William W. K. Zung at Duke University Medical Center in 1965, making it one of the earliest validated self-report measures of depression. Zung designed it to quantify depression based on a dimensional model, covering affective, physiological, psychomotor, and psychological symptoms across 20 items.
Each item is rated on a 4-point frequency scale (1–4). Ten items are negatively worded and scored directly; ten are positively worded and reverse-scored. The raw total (20–80) is converted to an SDS Index by multiplying by 100/80. An SDS Index of 50 or above indicates the presence of depression. The scale covers 20 characteristic signs and symptoms of depression, including sad affect, crying, sleep disturbance, appetite change, and hopelessness.
The Zung SDS is in the public domain and has been translated into over 30 languages. While the PHQ-9 is now more commonly used in primary care settings, the Zung SDS remains a reference standard in longitudinal research and is useful where a classic scale is required for comparison with historical data.
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Educational reference only. Cannot diagnose or replace clinical evaluation.
Zung SDS Interpretation
Zung (1965). SDS Index = (raw score / 80) × 100. Raw scores range from 20 to 80.
Track Depression Outcomes in HiBoop
Zung SDS alongside PHQ-9 and MADRS, longitudinal scoring to monitor treatment response across every patient.
Frequently Asked Questions
How is the Zung SDS scored?
Each of the 20 items is rated on a 4-point frequency scale (1 = a little of the time, 4 = most of the time). Ten positively worded items are reverse-scored. The raw total (20–80) is then converted to an SDS Index by multiplying by 100 and dividing by 80, yielding a score between 25 and 100.
What does a high Zung SDS score mean?
An SDS Index of 50 or above is the conventional threshold for clinically meaningful depressive symptoms. Scores of 50–59 are considered mild, 60–69 moderate to marked, and 70 or above severe. These ranges reflect commonly used clinical conventions established by Zung (1965) and should be interpreted by a qualified clinician.
Is the Zung SDS a self-report or clinician-administered scale?
The Zung SDS is a self-report questionnaire — respondents complete it independently, without clinician administration. This makes it practical for screening in primary care and research settings. A clinician should review results and conduct a full evaluation before making any diagnosis.
Can the Zung SDS diagnose depression?
No. The Zung SDS is a screening tool that quantifies the presence and severity of depressive symptoms; it cannot provide a diagnosis. A formal clinical evaluation, including a structured interview and review of history, is required for diagnosis. Biggs et al. (1978) confirmed the scale correlates well with clinician severity ratings, supporting its use as a research and monitoring instrument.
References
- 1.Zung WW. A self-rating depression scale. Arch Gen Psychiatry. 1965;12:63-70.View source
- 2.Biggs JT, Wylie LT, Ziegler VE. Validity of the Zung Self-rating Depression Scale. Br J Psychiatry. 1978;132:381-385.View source
- 3.Jokelainen J, Timonen M, Keinänen-Kiukaanniemi S, et al. Validation of the Zung self-rating depression scale (SDS) in older adults. Scand J Prim Health Care. 2019;37(3):353-357.View source
- 4.Ruiz-Grosso P, Loret de Mola C, Vega-Dienstmaier JM, et al. Validation of the Spanish Center for Epidemiological Studies Depression and Zung Self-Rating Depression Scales: a comparative validation study. PLoS One. 2012;7(10):e45413.View source
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Last reviewed: Jun 3, 2026
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