Zung Self-Rating Depression Scale (ZUNG)

Abstract

The Zung Self-Rating Depression Scale (ZSDS) is a concise, self-administered psychological scale designed to quantify the severity of depression in adult patients. Developed in 1965, the instrument consists of 20 items which evaluate four common characteristics of the condition, structured across four subscales: the core depressive factor, cognitive factor, anxiety factor, and somatic factor. The scale is suitable for use in diverse populations, including psychiatric inpatients and the elderly, serving primarily as a screening tool to measure the intensity of depressive symptomatology.

Keywords

Zung SDS, Self-Rating Depression Scale, Depression screening, Affective states, Self-report measure, Somatic symptoms, Factor analysis.

Authors

W.W. Zung

Purpose

The primary purpose of the ZSDS is to provide a rapid, quantitative measure of the intensity of depressive symptomatology experienced by an individual, typically referencing feelings over the past several days. It functions as an effective screening tool to assess the spectrum of depressive states, ranging from a normal mood profile to severe depression.

While highly effective in distinguishing depressed from non-depressed populations, the ZSDS is considered a non-diagnostically specific indicator. This means it assesses the overall severity of depressive symptoms and affective states, rather than providing a formal, specific clinical diagnosis based on classification systems like the DSM.

Construct

The ZSDS measures the psychological construct of clinical depression by assessing its behavioral, affective, and somatic manifestations. The scale is empirically derived to cover 20 items that load onto four distinct symptomatic dimensions, providing a comprehensive view of the patient’s depressed status.

The core dimensions assessed by the scale include:

• Core Depressive Factor: Items related to mood, feelings of despair, and overall emotional state (Items 1, 3, 6, 14, 17, 18, 19, 20).
• Cognitive Factor: Items assessing mental clarity, decision-making ability, and feelings of usefulness (Items 10, 11, 12, 16).
• Anxiety Factor: Items related to agitation, restlessness, and irritability (Items 4, 13, 15).
• Somatic Factor: Items addressing physiological symptoms such as weight change, constipation, and heart rate (Items 5, 7, 9).

Validity

The Zung Self-Rating Depression Scale demonstrates strong discriminant validity. Zung (1965) reported that depressed outpatients showed a significantly higher mean index score (0.74, equivalent to a total raw score of 59) compared to hospital staff control subjects (mean index score of 0.33, equivalent to 26), effectively discriminating between depressed and non-depressed samples.

Further validation by Guy (1976) indicated that while the scale is sensitive to depressive symptomatology, it is not diagnosis-specific. Mean total scores were highest for depressive disorders (65), but also elevated for other clinical groups such as anxiety disorders (53), schizophrenia (52), transient situational disorder (48), and personality disorders (56). This supports its role as a robust indicator of the severity of depressive symptoms across various psychiatric conditions.

Reliability

The ZSDS exhibits high estimates of reliability based on internal consistency statistics across various studies. A split-half reliability study conducted in a psychiatric population yielded a correlation coefficient (r) of 0.73 (Zung, 1972). This suggests consistent measurement within the clinical population.

In a large community survey of 1,173 subjects, Knight et al. (1983) found the internal consistency to be satisfactory, reporting a Cronbach’s alpha of 0.79. The validation work by Knight et al. (1983), conducted with 2,120 New Zealanders (aged 16 to 89), also noted that scores were inversely correlated with age, highlighting the importance of using specific and appropriate norms when assessing affective states, particularly across a wide age range.

Factor Analysis

The intended four-factor structure of the ZSDS has been empirically supported through factor analysis. Romera et al. (2008) examined the symptomatic dimensions of depression in 1,049 patients with major depressive disorder (MDD) in a primary care setting. Their analysis confirmed the four factors: core depressive factor, cognitive factor, anxiety factor, and somatic factor.

The study successfully validated the four-factor structure, obtaining high coefficients of congruence for each factor (0.98 for Factor I, 0.95 for Factor II, 0.92 for Factor III, and 0.87 for Factor IV). This strong structural validation confirms that the scale effectively measures distinct, yet related, components of depression.

Instrument

Test Type: Self-administered rating scale; Screening instrument for depressive symptomatology.

Format: 20 items rated on a 4-point Likert scale (ranging from “A little of the time” to “Most of the time”).

Language Available: English (Widely translated into other languages).

Population Group: Clinical and non-clinical adults, including psychiatric inpatients and the elderly.

Age Group: 16 years and older (Validated across a broad range, 16 to 89 years).

Population Details: Used in primary care, psychiatric settings, and community surveys for quick assessment of depressive status.

Test Methodology: Total raw scores range from 20 to 80. Scoring involves reverse-coding of positively worded items. The total score is often converted to an index score (Total Score / 80) for standardized interpretation.

Interpretation

Results consist of a total raw score (ranging from 20 through 80) as well as scores for the four underlying subscales. The average score historically reported for an individual with a depressive disorder is 65. The established clinical classification based on total scores is:

• 20-49: Normal Range
• 50-59: Mildly Depressed
• 60-69: Moderately Depressed
• 70 and above: Severely Depressed

Subscale scoring is calculated based on specific item groupings:

• The core depressive factor is computed from items 1, 3, 6, 14, 17, 18, 19, and 20 (Minimum score: 8; Maximum score: 32).
• The cognitive factor is computed from items 10, 11, 12, and 16 (Minimum score: 4; Maximum score: 16).
• The anxiety factor is computed from items 4, 13, and 15 (Minimum score: 3; Maximum score: 12).
• The somatic factor is computed from items 5, 7, and 9 (Minimum score: 3; Maximum score: 12).

Keywords

ZSDS, Mood disorders, Psychometrics, Self-report, Affective state, Clinical assessment, Geriatrics.

Authors

Author ORCID Identifier: Not provided.

Affiliation Email addresses: Not provided.

Correspondence Address: Not provided.

Permissions & Fee and Test Year

The Zung Self-Rating Depression Scale (ZSDS) was first published in 1965. It is generally recognized as a public domain instrument for non-commercial and academic use, though users should verify specific copyright restrictions, especially regarding commercial use or reproduction in digital formats.

Reference’s

• Knight, R. G., Waal-Manning, H. J., & Spears, G. (1983). Some norms and reliability data for the State-Trait Anxiety Inventory and the Zung Self-Rating Depression scale. British Journal of Clinical Psychology, 22(4), 245-249.
• Romera, I., Delgado-Cohen, H., Perez, T., Caballero, L., and Gilaberte, I. (2008). Factor analysis of the Zung self-rating depression scale in a large sample of patients with major depressive disorder in primary care. BMC Psychiatry, 8, 4.
• Zung, W. W. (1965). A self-rating depression scale. Archives of General Psychiatry, 12, 63-70.
• Zung, W. W. K., & Zung, E. M. (1986). Use of the Zung Self-Rating Depression Scale in the Elderly. Clinical Gerontologist, 5(1-2), 137-148.

Items of the Zung Self-Rating Depression Scale (ZUNG)

Instructions: Please read each statement and decide how much of the time the statement describes how you have been feeling during the past several days.

	A little of the time	Some of the time	Good part of the time	Most of the time
I feel down-hearted and blue	1	2	3	4
Morning is when I feel the best	4	3	2	1
I have crying spells or feel like it	1	2	3	4
I have trouble sleeping at night	1	2	3	4
I eat as much as I used to	4	3	2	1
I still enjoy sex	4	3	2	1
I notice that I am losing weight	1	2	3	4
I have trouble with constipation	1	2	3	4
My heart beats faster than usual	1	2	3	4
I get tired for no reason	1	2	3	4
My mind is as clear as it used to be	4	3	2	1
I find it easy to do the things I used to	4	3	2	1
I am restless and can’t keep still	1	2	3	4
I feel hopeful about the future	4	3	2	1
I am more irritable than usual	1	2	3	4
I find it easy to make decisions	4	3	2	1
I feel that I am useful and needed	4	3	2	1

	A little of the time	Some of the time	Good part of the time	Most of the time
My life is pretty full	4	3	2	1
I feel that others would be better off if I were dead	1	2	3	4
I still enjoy the things I used to do.	4	3	2	1