What is the difference between DASS (Depression Anxiety Stress Scales), Whooley, GAD (Generalized Anxiety Disorder), and PHQ (Patient Health Questionnaire)?

Comparison of Depression and Anxiety Screening Tools

These are distinct screening instruments that differ primarily in their length, scope, and clinical thresholds, with PHQ-9 and GAD-7 being the most widely recommended tools for depression and anxiety screening respectively.

PHQ-9 (Patient Health Questionnaire-9)

The PHQ-9 is the preferred first-line screening tool for depression. 1

• 9-item self-report scale assessing symptoms of major depressive disorder as defined by DSM-IV 1
• Scoring thresholds: 1-7 (minimal), 8-14 (moderate), 15-19 (moderate-to-severe), 20-27 (severe depressive symptomatology) 2
• Clinical action threshold: Score ≥8 requires further diagnostic assessment to identify the nature and extent of depressive symptoms 2, 3
• Domains assessed: Depressive symptoms and accompanying functional impairment 1
• Critical feature: Item 9 specifically assesses self-harm thoughts and requires immediate risk assessment if positive 2

Clinical Management Based on PHQ-9 Scores

• Scores 8-14: Consider low-intensity interventions such as guided self-help based on cognitive behavioral therapy or structured physical activity programs 2
• Scores ≥15: Refer to psychology and/or psychiatry for diagnosis and treatment 2, 3
• Any positive response to item 9: Immediate risk assessment warranted 2

GAD-7 (Generalized Anxiety Disorder-7)

The GAD-7 is the standard screening tool for anxiety disorders.

• 7-item self-report scale assessing probable causes of generalized anxiety disorder 1
• Scoring thresholds: ≥5 (mild), ≥10 (moderate), ≥15 (severe anxiety) 1, 2
• Domain assessed: GAD symptomatology specifically 1
• Clinical action threshold: Scores ≥10 warrant consideration of pharmacologic treatment such as SSRIs 2
• Broader utility: Detects not only generalized anxiety but also panic, social anxiety, and post-traumatic stress disorder 4

DASS (Depression Anxiety Stress Scales)

The DASS is a comprehensive tool measuring three distinct constructs but is less commonly used in routine clinical screening.

• Available in 21-item version (DASS-21) with three subscales: depression (7 items), anxiety (7 items), and stress (7 items) 5
• Key distinguishing feature: Omits somatic items and concentrates on psychological core aspects, making it particularly useful in pain patients where somatic symptoms may confound diagnosis 5
• Reliability: Depression subscale has Cronbach's alpha of at least 0.91, anxiety 0.78-0.82, stress 0.81-0.89 5
• Unique advantage: The stress subscale measures irritability and tension, which are important but underused aspects in pain assessment 5

Comparative Performance: DASS vs. PHQ/GAD

• DASS-Depression and PHQ-8 are highly correlated (r = 0.71) but PHQ-8 categorizes more individuals as having above-threshold depression (71.5% vs. 43.5%) 6
• DASS-Anxiety and GAD-7 are highly correlated (r = 0.61) but GAD-7 categorizes more individuals as having above-threshold anxiety (59.0% vs. 45.0%) 6
• Clinical implication: PHQ and GAD scales are more sensitive screening tools, while DASS may be more specific 6

Whooley Questions

The Whooley questions are an ultra-brief 2-item depression screener used for initial triage.

• Consists of the first two items of the PHQ-9: assessing anhedonia and depressed mood 3
• Screening algorithm: If either item scores ≥2, complete the full PHQ-9 assessment 3
• Purpose: Efficient first-step screening in busy clinical settings to identify who needs full assessment 3
• Also known as PHQ-2 with optimal cutpoint ≥3 for detecting depressive disorders 4, 7

Clinical Decision Algorithm

For Depression Screening:

1. Start with Whooley/PHQ-2 in all patients 3
2. If either item ≥2: Complete full PHQ-9 3
3. If PHQ-9 score 8-14: Initiate low-intensity interventions 2
4. If PHQ-9 score ≥15: Refer to mental health specialist 2

For Anxiety Screening:

1. Use GAD-7 as primary tool 1
2. If GAD-7 ≥10: Consider pharmacologic treatment or specialist referral 2
3. Alternative: GAD-2 (ultra-brief version) with cutpoint ≥3 for initial screening 7

Special Populations:

• Pain patients: Consider DASS-21 to avoid confounding from somatic symptoms 5
• When assessing both depression and anxiety: PHQ-9 and GAD-7 combination is preferred over DASS-21 for routine screening 6

Common Pitfalls to Avoid

• Failing to complete full PHQ-9 when initial Whooley questions are positive 3
• Omitting item 9 (self-harm assessment) from PHQ-9, which artificially lowers scores and misses critical risk 2, 3
• Not considering medical or substance-induced causes of symptoms before attributing to primary psychiatric disorder 2
• Applying incorrect cutoffs or misinterpreting severity thresholds across different scales 8
• Overlooking comorbidity: Approximately 31% of patients with anxiety disorder also have major depressive disorder 2