Zung Self-Rating Anxiety Scale (SAS)

Abstract

The Zung Self-Rating Anxiety Scale (SAS) is a 20-item self-administered psychometric assessment designed by psychiatrist William W. K. Zung in 1971 to quantify and evaluate the frequency and intensity of affective and somatic symptoms of anxiety. Rooted in clinical diagnostic criteria and neurovegetative manifestations of anxiety disorders, the scale operationalizes anxiety through a biopsychosocial lens, uniquely emphasizing autonomic, musculoskeletal, and cognitive-emotional markers. The instrument comprises 20 Likert-type items scored on a 4-point response continuum ranging from 1 (“A little of the time”) to 4 (“Most of the time”), yielding raw scores between 20 and 80. These raw scores are frequently converted into an anxiety index (SAS Index) ranging from 25 to 100 to standardize severity stratification across normal, mild-to-moderate, marked-to-severe, and extreme anxiety levels. Psychometric investigations spanning over five decades have consistently demonstrated robust internal consistency (Cronbach’s α typically ranging between .79 and .92 across diverse psychiatric, medical, and non-clinical cohorts) and exceptional test-retest reliability ($r = .81$ to $.94$). Criterion and convergent validity analyses demonstrate robust correlations with established clinician-rated and self-report measures, including the Hamilton Anxiety Rating Scale (HAM-A), the Beck Anxiety Inventory (BAI), and the State-Trait Anxiety Inventory (STAI). Confirmatory factor analyses reveal multidimensional underlying structures typically characterized by autonomic hyperarousal, motor tension, cognitive apprehension, and central nervous system disturbances. This article provides a comprehensive academic analysis of the SAS, detailing its historical provenance, theoretical and empirical framework, operational constructs, psychometric parameters, structural models, and operational scoring methodologies.

Keywords

Zung Self-Rating Anxiety Scale, SAS, William W. K. Zung, anxiety assessment, autonomic hyperarousal, somatic symptoms, psychometrics, factor analysis, anxiety index, clinical screening

Authors

The Zung Self-Rating Anxiety Scale was conceived, developed, and clinically validated by William Wen-Kwai Zung, M.D. (1929–1992). At the time of the instrument’s formulation, Dr. Zung was a Professor of Psychiatry at the Duke University Medical Center and a staff psychiatrist at the Veterans Administration Hospital in Durham, North Carolina, United States.

Dr. Zung was a pioneer in quantitative psychopathology and clinical psychometrics during the mid-twentieth century. Recognizing the acute clinical need for standardized, cost-effective, and rapid patient-reported outcome measures, he developed several milestone psychological assessment tools, most notably the Zung Self-Rating Depression Scale (SDS) in 1965, followed by its complementary counterpart, the Zung Self-Rating Anxiety Scale (SAS), in 1971. His scholarly trajectory focused heavily on affective disorders, sleep architecture alterations in psychiatric illness, psychopharmacological efficacy trials, and cross-cultural psychiatric epidemiological methods. Inquiries regarding Dr. Zung’s historical archives and archival psychometric datasets are preserved through the Department of Psychiatry and Behavioral Sciences at Duke University Medical Center.

Purpose

The primary clinical and empirical objective of the Zung Self-Rating Anxiety Scale is to provide an objective, rapid, and empirically grounded operationalization of anxiety severity in adult and adolescent populations. During the late 1960s and early 1970s, diagnostic assessment in psychiatry relied predominantly on unstructured clinical interviews or extensive, clinician-administered rating tools such as the Hamilton Anxiety Rating Scale (HAM-A). While clinician-administered instruments provided rich clinical insight, they required extensive training, suffered from inter-rater subjectivity, and were prohibitively time-consuming for large-scale epidemiological investigations, rapid clinical triaging, and routine pharmacotherapeutic monitoring. Dr. Zung formulated the SAS to resolve these limitations by constructing a patient-centered instrument that captures the full spectrum of subjective suffering associated with pathological anxiety.

Pathological anxiety manifests as an intricate interplay between cognitive vigilance, affective distress, neuromuscular tension, and autonomic hyperactivity. Many prevailing scales of the era leaned disproportionately toward cognitive worrying or general neurotic distress. Zung sought to rectify this disequilibrium by constructing an instrument that gave equal, rigorous diagnostic weight to the visceral, somatic, and autonomic manifestations of anxiety. Because patients presenting to general medical settings, primary care clinics, and emergency departments frequently express anxiety through functional somatic complaints—such as palpitations, dyspnea, tremors, lightheadedness, and gastrointestinal distress—the SAS serves as a critical bridge between somatic medicine and clinical psychiatry.

In clinical practice, the SAS functions as a frontline triage mechanism for detecting undiagnosed generalized anxiety disorder (GAD), panic disorder, and acute situational stress reactions. It aids clinicians in tracking longitudinal therapeutic trajectories, calibrating dosages of anxiolytic medications (such as selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, or benzodiazepines), and evaluating responses to evidence-based psychotherapy, notably cognitive behavioral therapy (CBT). In psychopharmacological and clinical research, the SAS acts as a standardized endpoint measure, permitting cross-study meta-analytic comparisons and multi-site clinical trial harmonization across worldwide medical centers.

Psychological Construct

The construct assessed by the Zung Self-Rating Anxiety Scale is dimensional anxiety, conceptualized as a multi-system biological and psychological response to perceived threat or diffuse apprehension. Unlike trait constructs that evaluate enduring personality predispositions, the SAS operationalizes state-related anxiety severity over recent timeframes, measuring the current clinical burden of symptomatology across four foundational diagnostic domains:

1. Cognitive and Affective Manifestations

This dimension encompasses the core experiential, emotional, and cognitive perturbations characteristic of anxiety disorders. Items evaluating this domain capture free-floating apprehension, mental disorganization, anticipatory panic, and catastrophizing ideation:

• Item 1 (“I feel more nervous and anxious than usual”): Measures subjective subjective nervousness and elevated baseline anxiety relative to baseline functioning.
• Item 2 (“I feel afraid for no reason at all”): Captures unprompted, spontaneous dread and generalized apprehension unanchored to identifiable environmental stimuli.
• Item 3 (“I get upset easily or feel panicky”): Evaluates emotional lability, lowered frustration tolerance, and episodic panic reactivity.
• Item 4 (“I feel like I’m falling apart and going to pieces”): Gauges severe psychological disintegration, cognitive fragmentation, and the acute terror of losing emotional equilibrium.
• Item 5 (“I feel that everything is all right and nothing bad will happen”): A reverse-scored item operationalizing optimism, subjective safety, and the absence of catastrophic anticipation.

2. Autonomic and Cardiovascular Hyperarousal

The autonomic nervous system, specifically the sympathetic branch, displays dramatic hyperactivity during anxious states. The SAS places profound diagnostic emphasis on these physiological manifestations, which are central to the diagnostic criteria of panic attacks and hyperarousal states:

• Item 10 (“I can feel my heart beating fast”): Taps into tachycardia, sinus palpitations, and heightened interoceptive awareness of cardiac acceleration.
• Item 11 (“I am bothered by dizzy spells”): Assesses vestibular instability, orthostatic sensations, and transient cerebral hypoperfusion secondary to hyperventilation.
• Item 12 (“I have fainting spells or feel like it”): Evaluates vasovagal instability and severe autonomic distress culminating in presyncope.
• Item 18 (“My face gets hot and blushes”): Assesses peripheral vasomotor flushes and sympathetic cutaneous vascular dilation.
• Item 17 (“My hands are usually dry and warm”): A reverse-scored indicator measuring peripheral vasomotor constriction; sympathetic arousal typically induces cold, clammy extremities due to vasoconstriction.

3. Sensorimotor and Musculoskeletal Tension

Chronic anxiety induces tonic motor preparedness, reflecting the biological motor programs of the fight-or-flight response. The musculoskeletal sub-dimension assesses both observable motor agitation and subjective muscle pain:

• Item 6 (“My arms and legs shake and tremble”): Measures visible kinetic tremors and somatic muscular oscillation resulting from adrenergic surge.
• Item 7 (“I am bothered by headaches neck and back pain”): Evaluates chronic sustained contraction of the trapezius, cervical, and frontalis muscles, generating tension-type cephalalgia and axial discomfort.
• Item 8 (“I feel weak and get tired easily”): Measures neuromuscular exhaustion, physical fatigue, and energy depletion following prolonged motor bracing.
• Item 9 (“I feel calm and can sit still easily”): A reverse-scored index of motoric serenity, postural stability, and the absence of psychomotor agitation or akathisia.

4. Central Nervous System and Visceral Disruption

Anxiety reverberates across broad neurobiological systems, impairing homeostatic sleep architecture, respiratory patterns, gastrointestinal motility, and sensory processing:

• Item 13 (“I can breathe in and out easily”): A reverse-scored marker of respiratory competence, evaluating the presence of dyspnea, thoracic constriction, or hyperventilation sensations.
• Item 14 (“I get numbness and tingling in my fingers and toes”): Evaluates acroparesthesia, a classic physiological hallmark of hypocapnia induced by psychogenic hyperventilation.
• Item 15 (“I am bothered by stomach aches or indigestion”): Measures functional gastrointestinal distress, enteric nervous system dysregulation, nausea, and epigastric discomfort mediated by the gut-brain axis.
• Item 16 (“I have to empty my bladder often”): Assesses urinary urgency and pollakiuria resulting from detrusor muscle hyperexcitability under central sympathetic driving.
• Item 19 (“I fall asleep easily and get a good night’s rest”): A reverse-scored item evaluating initial insomnia, sleep fragmentation, and overall sleep architecture integrity.
• Item 20 (“I have nightmares”): Measures rapid eye movement (REM) sleep disturbance, nocturnal autonomic surges, and anxiety-laden dream mentation.

Theoretical Framework

The theoretical architecture of the Zung Self-Rating Anxiety Scale is grounded in the biopsychosocial and psychobiological models of anxiety that matured throughout the mid-twentieth century. Zung rejected purely psychoanalytic or purely behavioral models, advocating instead for an integrative medical-psychiatric framework wherein anxiety is conceptualized as an integrated biological reaction involving affective experience, cognitive appraisal, and widespread neurovegetative discharges.

1. The Cannon-Selye Stress and Autonomic Activation Paradigm

The foundational bedrock of the SAS draws heavily upon Walter Cannon’s physiological formulations of the acute fight-or-flight response and Hans Selye’s General Adaptation Syndrome (GAS). Under this framework, anxiety represents an organized neuroendocrine adaptation coordinated via the sympathetic-adrenomedullary (SAM) axis and the hypothalamic-pituitary-adrenal (HPA) axis. When threat is perceived, the amygdaloid complex stimulates brainstem nuclei, notably the locus coeruleus (noradrenergic pathways) and the nucleus tractus solitarius, driving autonomic outflows. The prominent representation of visceral symptoms in the SAS—tachycardia, tachypnea, acroparesthesia, diaphoresis, and visceral motility alterations—directly operationalizes this peripheral cascade of catecholaminergic discharge.

2. Cognitive-Appraisal and Cybernetic Feedback Loops

While biological arousal constitutes the physiological substrate, Zung embedded the cognitive appraisal model later articulated by Aaron Beck and Richard Lazarus. The cognitive manifestations in the SAS (fear of falling apart, unprompted apprehension, and perceived threat) are not isolated phenomena; they form recursive, cybernetic feedback loops with somatic sensations. Interoceptive conditioning mechanisms—wherein benign somatic fluctuations (e.g., sinus tachycardia or lightheadedness) are misappraised as imminent catastrophes (e.g., myocardial infarction, syncope, or madness)—amplify physiological hyperarousal. By capturing both the catastrophic cognitive thoughts (Items 2, 4) and the visceral cues (Items 10, 11, 12, 14), the SAS mirrors the modern cognitive-behavioral understanding of the panic cycle.

3. Operational Diagnostic Parallels with Modern Nosologies

Constructed in an era preceding the DSM-III revolution of 1980, the SAS prefigured modern operationalized nosology. Zung’s systematic inclusion of affective, motor, autonomic, and central nervous system criteria anticipated the diagnostic criteria later standardized in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) and the International Classification of Diseases (ICD-11) for Generalized Anxiety Disorder and Panic Disorder. Zung’s balanced psychometric design—incorporating 15 negatively worded (symptom present) items and 5 positively worded (symptom absent) reverse-scored items—was methodologically engineered to attenuate acquiescence response bias and verify respondent attentiveness.

Validity

The psychometric validity of the Zung Self-Rating Anxiety Scale has been established through empirical research spanning psychiatric cohorts, medical patients, community populations, and cross-cultural validation studies.

Construct and Convergent Validity

Convergent validity has been evaluated by correlating SAS indices with established, clinician-administered and self-report instruments. In his initial validation work (Zung, 1971), Zung administered the SAS alongside clinician ratings using a structured interview protocol matching the 20 criteria. In a sample of patients diagnosed with anxiety disorders, patients displayed a mean SAS index of $64.0 \pm 11.2$, which was significantly elevated compared to normal control participants ($33.8 \pm 5.9$, $p < .001$), demonstrating excellent construct differentiation.

Subsequent psychometric studies have confirmed high concurrent correlations with modern standard rating scales:

• Hamilton Anxiety Rating Scale (HAM-A): Correlation coefficients typically range between $r = .65$ and $r = .83$, establishing strong concurrent congruence between patient self-reports on the SAS and independent clinical interviews.
• Beck Anxiety Inventory (BAI): Because the BAI also loads heavily on somatic and panic-related symptoms, correlations between the SAS and BAI are high ($r = .72$ to $.86$).
• State-Trait Anxiety Inventory (STAI): SAS indices correlate moderately-to-strongly with STAI State anxiety ($r = .68$ to $.78$) and STAI Trait anxiety ($r = .55$ to $.70$).

Discriminant and Divergent Validity

Discriminant validity addresses whether the SAS can distinguish anxiety from related but theoretically distinct constructs, particularly major depressive disorder. Because of high comorbidity and overlapping distress markers between anxiety and depression, bivariate correlations between the SAS and the Zung Self-Rating Depression Scale (SDS) or the Beck Depression Inventory (BDI) often range from $r = .50$ to $.68$. However, factor analytic extractions demonstrate that when non-somatic cognitive items are isolated, the SAS somatic-autonomic factor exhibits distinct divergence from depressive anhedonia and cognitive hopelessness, confirming adequate discriminative integrity.

Criterion, Sensitivity, and Specificity Evidence

Receiver Operating Characteristic (ROC) curve analyses across psychiatric outpatient and primary care populations highlight the clinical diagnostic utility of the SAS. Using a raw score cut-off of 45 (corresponding to a SAS Index of approximately 56), the instrument demonstrates sensitivity indices ranging between 82% and 89% and specificity values between 78% and 86% for identifying patients meeting DSM criteria for generalized anxiety disorder or panic disorder. In specialized populations, such as adults with intellectual disabilities (Ramirez & Lukenbill, 2008), adapted formats (SAS-ID) demonstrated that the core items maintain their discriminative capacity for identifying clinically significant anxiety disorders.

Reliability

The reliability of the Zung Self-Rating Anxiety Scale has been established through internal consistency assessments, split-half metrics, and test-retest longitudinal analyses across global research cohorts.

Internal Consistency

Internal consistency metrics evaluate the degree of interrelatedness among the 20 items. Across extensive psychometric literature:

• Cronbach’s Alpha (α): Alpha coefficients for the global scale typically fall between $.79$ and $.92$. In Zung’s original cohorts, split-half reliability yielded a Spearman-Brown corrected coefficient of $.71$ to $.84$. Modern validations in large non-clinical cohorts (e.g., college students and community adults) report Cronbach’s α values centered around $.82–.86$, while clinical psychiatric samples routinely demonstrate α values exceeding $.88$.
• Item-Total Correlations: Corrected item-total correlations for the majority of items range between $.38$ and $.68$. Somatic items directly reflecting autonomic discharge (e.g., Item 10: heart beating fast; Item 6: shaking/trembling; Item 11: dizzy spells) exhibit strong item-total correlations ($r > .50$). Reverse-scored items (Items 5, 9, 13, 17, and 19) occasionally demonstrate lower item-total correlations ($r = .28–.45$), reflecting cognitive response-reversal effects rather than theoretical invalidity.

Test-Retest Stability

Because the SAS is designed to measure clinical severity—which naturally fluctuates in response to life events, spontaneous recovery, or therapeutic intervention—test-retest reliability is evaluated over short timeframes (e.g., 24 hours to two weeks) in untreated, stable cohorts. Studies using a 1- to 2-week test-retest design report intraclass correlation coefficients (ICC) and Pearson correlation coefficients ($r$) ranging between $.81$ and $.94$, demonstrating high temporal stability in the absence of clinical intervention.

Standard Error of Measurement and Precision

The Standard Error of Measurement (SEM) for the SAS raw score is calculated to be between $2.8$ and $3.5$ score points across multiple studies. This indicates that an individual’s observed raw score can be interpreted with a 95% confidence interval spanning approximately $\pm 6$ points, providing psychometric precision for assessing therapeutic improvement or relapse.

Factor Analysis

Extensive exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) studies have evaluated the latent dimensionality of the SAS across various cultures, medical settings, and clinical cohorts.

Exploratory Factor Solutions

Although Zung initially conceived the scale as an operationalization of a single construct of general anxiety divided into four theoretical symptom domains, empirical factor extractions typically reveal a multidimensional latent structure comprising between two and five distinct factors:

• Factor 1: Autonomic / Somatic Hyperarousal: Explaining the largest portion of total variance (often 25%–35%), this factor is anchored by high loadings from Item 10 (tachycardia, $lambda = .65–.78$), Item 11 (dizziness, $lambda = .58–.72$), Item 12 (fainting, $lambda = .52–.69$), Item 14 (numbness/tingling, $lambda = .48–.65$), and Item 18 (facial flushing, $lambda = .45–.62$).
• Factor 2: Cognitive and Affective Apprehension: Characterized by robust loadings on Item 1 (nervousness, $lambda = .62–.75$), Item 2 (unprompted fear, $lambda = .68–.80$), Item 3 (panicky/easily upset, $lambda = .55–.70$), and Item 4 (falling apart, $lambda = .58–.74$).
• Factor 3: Motoric Tension and Physical Fatigue: Encompassing Item 6 (trembling, $lambda = .54–.71$), Item 7 (musculoskeletal pain, $lambda = .42–.60$), and Item 8 (weakness/fatigue, $lambda = .45–.64$).
• Factor 4: Central Nervous System / Somatosensory Deregulation: Comprising sleep disturbances (Item 19, Item 20) and visceral disruptions (Item 15, Item 16).
• Methodological Reverse-Scoring Factor: In some four- or five-factor solutions, the five reverse-scored items (5, 9, 13, 17, 19) load together on a shared method-related factor, a common phenomenon in psychometrics attributable to cognitive shift when interpreting positively framed items.

Confirmatory Factor Analytic Fit Indices

Confirmatory factor analytic investigations comparing a strictly unidimensional model against hierarchical and correlated four-factor models have consistently confirmed the superiority of multidimensional solutions. Across international cohorts (e.g., European, East Asian, and North American samples), the correlated four-factor model exhibits acceptable to excellent goodness-of-fit indices:

• Comparative Fit Index (CFI): Values routinely exceed $.91–.95$, denoting robust structural fit.
• Tucker-Lewis Index (TLI): Typically ranges from $.90$ to $.94$.
• Root Mean Square Error of Approximation (RMSEA): Estimates regularly register between $.042$ and $.063$, falling well below the conventional $.08$ ceiling for satisfactory model approximation.
• Standardized Root Mean Square Residual (SRMR): Observed between $.038$ and $.055$.

These structural findings affirm that while the global SAS score accurately indexes overall anxiety severity, clinicians and researchers can interpret subscale scores reflecting somatic hyperarousal and cognitive apprehension.

Instrument / Measurement Tool

The Zung Self-Rating Anxiety Scale is a standardized, self-administered clinical psychometric instrument. Its operational characteristics are summarized below:

• Test Type: Standardized self-report inventory (patient-reported outcome measure).
• Format: Paper-and-pencil or computer-administered questionnaire.
• Number of Items: 20 items.
• Response Scale: 4-point Likert-type frequency scale:
  • 1: A little of the time
  • 2: Some of the time
  • 3: Good part of the time
  • 4: Most of the time
• Administration Time: Approximately 5 to 10 minutes.
• Target Population: Adolescents and adults (ages 12 and older); validated adaptations are available for specialized populations, including individuals with intellectual disabilities (SAS-ID).
• Scoring Protocol:
  • Direct Scoring: 15 items phrased toward anxiety symptoms (Items 1, 2, 3, 4, 6, 7, 8, 10, 11, 12, 14, 15, 16, 18, 20) are scored directly from 1 to 4: 1 = “A little of the time”, 2 = “Some of the time”, 3 = “Good part of the time”, 4 = “Most of the time”.
  • Reverse Scoring: 5 items framed positively as indications of calmness or the absence of anxiety (Items 5, 9, 13, 17, 19) are reverse-scored: 4 = “A little of the time”, 3 = “Some of the time”, 2 = “Good part of the time”, 1 = “Most of the time”.
  • Raw Score Range: Sum of all 20 items yields a raw score ranging from 20 to 80.
  • Anxiety Index (SAS Index) Calculation: In many clinical and research contexts, the raw score is transformed into a percentage-based index using the formula:$$\text{SAS Index} = \left( \frac{\text{Raw Score}}{80} \right) \times 100$$The index ranges from 25 to 100.
• Diagnostic Severity Interpretive Cut-Offs:
  • Raw Score 20–44 (Index < 50): Normal Range (no clinically significant anxiety).
  • Raw Score 45–59 (Index 50–59): Mild to Moderate Anxiety Levels.
  • Raw Score 60–74 (Index 60–74): Marked to Severe Anxiety Levels.
  • Raw Score 75–80 (Index 75 and above): Extreme Anxiety Levels.

Permissions & Fee and Test Year

The Zung Self-Rating Anxiety Scale was originally published in 1971 in the journal Psychosomatics (Zung, 1971). Dr. William W. K. Zung published the instrument with the explicit clinical intention of providing a widely accessible, unencumbered assessment tool for the scientific and medical communities.

In contemporary practice, the original 20-item instrument is considered to reside in the public domain for non-commercial academic research, clinical education, and standard individual clinical evaluation. No licensing fees or royalty payments are owed for standard clinical and non-profit research utilization. Commercial applications, inclusion in proprietary digital health software suites, or corporate clinical trial platforms may be subject to institutional reproduction permissions governed by original publishing copyright agreements or academic executor estates. Researchers administering translated iterations are encouraged to cite Dr. Zung’s original 1971 validation paper and reference corresponding cultural adaptation literature.

References

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• Beck, A. T., Epstein, N., Brown, G., & Steer, R. A. (1988). An inventory for measuring clinical anxiety: Psychometric properties. Journal of Consulting and Clinical Psychology, 56(6), 893–897. https://doi.org/10.1037/0022-006X.56.6.893
• Dunstan, D. A., & Scott, N. (2020). Norms for Zung’s Self-rating Anxiety Scale. BMC Psychiatry, 20(1), Article 70. https://doi.org/10.1186/s12888-019-2428-1
• Dunstan, D. A., Scott, N., & Todd, A. K. (2017). Screening for anxiety and depression: Reassessing the utility of the Zung scales. BMC Psychiatry, 17(1), Article 329. https://doi.org/10.1186/s12888-017-1489-6
• Hamilton, M. (1959). The assessment of anxiety states by rating. British Journal of Medical Psychology, 32(1), 50–55. https://doi.org/10.1111/j.2044-8341.1959.tb00467.x
• Olatunji, B. O., Deacon, B. J., Abramowitz, J. S., & Tolin, D. F. (2006). Dimensionality of somatic anxiety: Evaluation of the Beck Anxiety Inventory and the Zung Self-Rating Anxiety Scale. Journal of Anxiety Disorders, 20(5), 543–569. https://doi.org/10.1016/j.janxdis.2005.06.002
• Ramirez, S., & Lukenbill, J. (2008). Psychometric properties of the Zung Self-Rating Anxiety Scale for adults with intellectual disabilities (SAS-ID). Journal of Developmental and Physical Disabilities, 20(6), 573–580. https://doi.org/10.1007/s10882-008-9121-6
• Spielberger, C. D., Gorsuch, R. L., Lushene, R., Vagg, P. R., & Jacobs, G. A. (1983). Manual for the State-Trait Anxiety Inventory (Form Y). Consulting Psychologists Press.
• Zung, W. W. K. (1965). A self-rating depression scale. Archives of General Psychiatry, 12(1), 63–70. https://doi.org/10.1001/archpsyc.1965.01720310065008
• Zung, W. W. K. (1971). A rating instrument for anxiety disorders. Psychosomatics, 12(6), 371–379. https://doi.org/10.1016/S0033-3182(71)71479-0
• Zung, W. W. K. (1979). Assessment of anxiety disorder: New rating scales. Psychosomatics, 20(6), 414–418. https://doi.org/10.1016/S0033-3182(79)70792-4

13. Items of the Scale (Questionnaire)