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DASS-21

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Overview

The Depression Anxiety Stress Scales - Short Form (DASS-21) is a validated self-report instrument for the simultaneous assessment of depression, anxiety, and stress. The instrument was developed by Lovibond & Lovibond (1995) at the University of New South Wales (UNSW) and is designed as the short form of the 42-item full version (DASS-42).

Key Properties:

• 21 items on a 4-point Likert scale (0-3)
• 3 subscales with 7 items each: Depression, Anxiety, Stress
• Time frame: Past week
• License: Public domain – freely available without license fees
• German Validation: Nilges & Essau (2015)
• Administration: 5-10 minutes

Questionnaire Structure

Response Scale (4-Point Likert)

Subscales and Item Assignment

Score Calculation

Raw Scores (DASS-21)

For each subscale, the sum of the 7 associated items is calculated:

Raw Score = Sum of 7 item responses (Range: 0-21)

DASS-42 Equivalents

Since the published severity cut-offs are based on the DASS-42 full version, the DASS-21 raw scores are multiplied by 2:

DASS-42 Equivalent = DASS-21 Raw Score x 2 (Range: 0-42)

Severity Cut-offs (DASS-42 Equivalents)

Severity Cut-offs (DASS-21 Raw Scores)

FHIR Implementation

Language Strategy: The DASS-21 is implemented with English as the primary language, as the original version of the instrument was written in English. German translations according to Nilges & Essau (2015) are provided as Translation extensions.

Terminology Strategy: The DASS-21 implementation uses MII-controlled terminology (no LOINC codes), as LOINC currently does not provide complete DASS-21 codings. The SNOMED CT codes 416954004 |Depression anxiety stress scales depression score| and 416767005 |Depression anxiety stress scales stress score| are used for score coding.

Questionnaire

Canonical URL: https://www.medizininformatik-initiative.de/fhir/ext/modul-pro/Questionnaire/mii-qst-pro-dass-dass21

Implemented Capabilities:

• Displayable, Collectable, Calculatable, Extractable, Domain-aligned

Key Features:

• Automatic score calculation via FHIR variables and FHIRPath
• 6 calculated score items: 3 raw scores + 3 DASS-42 equivalents
• MII CodeSystem with ordinalValue extensions for scoring

See the Questionnaire definition for the full resource.

CodeSystem and ValueSet

CodeSystem: mii-cs-pro-dass-21 – Item codes and response scale with English primary texts and German translations (Nilges & Essau 2015)

See the CodeSystem definition for the full resource.

ValueSet: mii-vs-pro-dass-21-answer-list – 4-point Likert response scale (0-3)

See the ValueSet definition for the full resource.

Score Representation

The DASS-21 generates 6 scores at two levels:

Raw Scores (DASS-21, Range 0-21):

• Depression Raw Score (mii-obsdef-pro-score-dass21-depression-raw) – SNOMED: 416954004
• Anxiety Raw Score (mii-obsdef-pro-score-dass21-anxiety-raw)
• Stress Raw Score (mii-obsdef-pro-score-dass21-stress-raw) – SNOMED: 416767005

DASS-42 Equivalents (Raw Score x 2, Range 0-42):

• Depression Equivalent (mii-obsdef-pro-score-dass21-depression-equiv) – SNOMED: 416954004
• Anxiety Equivalent (mii-obsdef-pro-score-dass21-anxiety-equiv)
• Stress Equivalent (mii-obsdef-pro-score-dass21-stress-equiv) – SNOMED: 416767005

Scoring Implementation

Automatic score calculation via FHIR variables and SDC calculatedExpression:

// FHIRPath - Variable: depressionRaw
%resource.item.where(linkId.matches('^dass-dass21-q(03|05|10|13|16|17|21)$')).answer.value.ordinal().sum()

// FHIRPath - Variable: anxietyRaw
%resource.item.where(linkId.matches('^dass-dass21-q(02|04|07|09|15|19|20)$')).answer.value.ordinal().sum()

// FHIRPath - Variable: stressRaw
%resource.item.where(linkId.matches('^dass-dass21-q(01|06|08|11|12|14|18)$')).answer.value.ordinal().sum()

// DASS-42 Equivalent (Example Depression)
%depressionRaw * 2

Psychometric Properties

Internal Consistency

• Depression: Cronbach's alpha = 0.88 (German version, Nilges & Essau 2015)
• Anxiety: Cronbach's alpha = 0.76
• Stress: Cronbach's alpha = 0.86

Factor Structure

• Confirmatory 3-factor model with good fit
• Clear assignment of items to Depression, Anxiety, and Stress
• Discriminant validity between the three subscales

Clinical Use

• Screening: Simultaneous assessment of depression, anxiety, and stress
• Progress Monitoring: Sensitivity to change over time
• Differential Diagnostics: Differentiation between affective and anxiety disorders
• Research: Broad application in clinical and epidemiological studies

Domain Alignment

The DASS-21 subscales are assigned to the following health domains:

References

1. Lovibond SH, Lovibond PF. (1995) Manual for the Depression Anxiety Stress Scales (2nd ed.) Sydney: Psychology Foundation of Australia

2. Nilges P, Essau C. (2015) Die Depressions-Angst-Stress-Skalen: Der DASS – ein Screeninginstrument nicht nur fur Schmerzpatienten Schmerz. 29(6):649-57

3. Bibi A, Lin M, Zhang XC, Margraf J. (2020) Psychometric properties and measurement invariance of Depression, Anxiety and Stress Scales (DASS-21) across cultures International Journal of Psychology. 55(6):916-925

This implementation follows the MII terminology strategies and uses MII CodeSystems for score calculations. The DASS-21 is public domain and can be used without license fees.