Interactive Interpreter

Zung SDS: Self-Rating Depression Scale

The Zung SDS (Zung Self-Rating Depression Scale) is a 20-item self-report questionnaire that measures affective, somatic, psychomotor and psychological symptoms of depression. The raw total converts to an SDS Index of 25–100, with 50 or above conventionally indicating clinically meaningful depressive symptoms.

For professional reference, research, and education only. Not for diagnosis or medical advice.

Zung SDS Score Interpreter

  • Enter a total score to see its range.

  • 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 IndexInterpretation
    70+Severe depressionSDS Index ≥70 corresponds to severe depressive symptoms.
    60–69Moderate depressionSDS Index 60–69 corresponds to moderate to marked depressive symptoms.
    50–59Mild depressionSDS Index 50–59 corresponds to mild to moderate depressive symptoms.
    25–49Normal 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.

The Zung SDS (Zung Self-Rating Depression Scale) is a 20-item self-report questionnaire that measures symptoms of depression, first published in 1965 [1]. Scores are expressed as an SDS Index from 25 to 100, and an Index of 50 or above is the usual threshold for clinically meaningful depressive symptoms.

What does the Zung SDS measure?

The Zung SDS was developed by William Zung and published in 1965, making it one of the earlier self-report measures of depression [1]. Its 20 items cover affective, physiological, psychomotor and psychological symptoms, including sad affect, crying, sleep disturbance, appetite change and hopelessness.

Later studies found it a valid and sensitive measure of clinical severity in depressed adults [2].

Check the copyright holder's terms before clinical or commercial use. The PHQ-9 is now more commonly used in primary care; the Zung SDS is useful where comparison with older research data is needed.

How do you give the Zung SDS?

The Zung SDS is a self-report questionnaire that respondents complete independently, without clinician administration, which makes it practical for screening in primary care and research. Each of the 20 statements is rated on a 4-point frequency scale from 1 (a little of the time) to 4 (most of the time). A clinician should review the results before any diagnostic conclusion.

Rate how each statement applies to you right now or over the past several days.

Educational reference only. Cannot diagnose or replace clinical evaluation.

How do you score and interpret the Zung SDS?

  • Item scoring. Each item is rated 1 to 4. Ten items are negatively worded and scored directly; ten are positively worded and reverse-scored.
  • Raw score. The 20 items sum to a raw score from 20 to 80.
  • SDS Index. The raw score is converted to an Index: (raw score / 80) × 100, giving 25 to 100.

Use the score interpreter above to look up an Index: below 50 is the normal range, 50–59 mild, 60–69 moderate to marked and 70 or above severe. These ranges are a commonly used clinical convention.

Psychometric properties

  • Validity [2]: In 26 depressed outpatients treated with a tricyclic antidepressant, the Zung SDS correlated 0.69 with the treating physician's global rating; in 41 adults it correlated highly with the Hamilton Rating Scale, and it distinguished four severity groups.
  • Spanish version [4]: In 194 adults in Lima, Peru, Cronbach's alpha was 0.89 and the area under the ROC curve was 0.84 for separating major depression from other psychiatric disorders and 0.96 for separating it from no psychiatric disorder (optimal cut-offs, as reported in that study, of ≥47 and ≥45).
  • Older adults [3]: In 520 community-dwelling adults aged 72–73 in Finland, the area under the curve was 0.85; the optimal cut-off point of 39 gave a sensitivity of 79.2% and specificity of 72.2%, with a positive predictive value of 12.5% and a negative predictive value of 98.6%.

Limitations

  • Screening, not diagnosis. The Zung SDS quantifies depressive symptoms; a diagnosis needs a clinical evaluation.
  • Cutoffs vary. Optimal cut-offs differ across languages, ages and settings, and the Index bands are a convention.
  • Low positive predictive value in community samples. In older community adults, most positive screens were false positives (PPV 12.5%) [3].
  • Self-report. Results depend on the respondent's recall and candour.

For individuals: This page is a clinical reference, not a diagnostic tool. If you have concerns about your own symptoms, bring this information to a qualified mental health professional.

FAQ

  • 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 are a commonly used clinical convention 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. A validation study found that it correlates well with clinician severity ratings, supporting its use as a research and monitoring tool.

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