PHQ-9 vs GAD-7: when to use each scale

Important clinical note: This article is educational in nature. Interpreting psychometric scales requires specialized clinical training. The cut-off scores indicated are general reference points; clinical decisions always integrate multiple sources of information. This content does not replace professional care.

The PHQ-9 and GAD-7 are two of the most widely used screening scales in clinical psychology and primary care worldwide. They are brief, validated in multiple languages, and sensitive to change over time. But using them well requires understanding what each one measures, what it does not measure, and in which clinical situations it makes sense to use both.

What the PHQ-9 measures

The PHQ-9 (Patient Health Questionnaire-9) evaluates the presence and intensity of depressive symptoms over the past two weeks. Its nine items correspond directly to the DSM-5 diagnostic criteria for major depressive episode:

1. Anhedonia (loss of interest or pleasure)
2. Depressed mood
3. Sleep disturbances
4. Fatigue or loss of energy
5. Changes in appetite or weight
6. Feelings of worthlessness or excessive guilt
7. Concentration difficulties
8. Psychomotor slowing or agitation
9. Thoughts of death or suicidal ideation

Item 9 makes the PHQ-9 a risk detection tool in addition to a symptom screening instrument.

PHQ-9 cut-off scores:

Score	Severity
1-4	Minimal
5-9	Mild
10-14	Moderate
15-19	Moderately severe
20-27	Severe

A score of 10 or above is the most commonly used threshold for initiating a full diagnostic evaluation or considering treatment.

What the GAD-7 measures

The GAD-7 (Generalized Anxiety Disorder-7) evaluates generalized anxiety symptoms over the past two weeks. Its seven items cover:

1. Feeling nervous, anxious, or on edge
2. Not being able to stop or control worrying
3. Worrying too much about different things
4. Trouble relaxing
5. Being so restless it is hard to sit still
6. Becoming easily annoyed or irritable
7. Feeling afraid as if something awful might happen

GAD-7 cut-off scores:

Score	Severity
1-4	Minimal
5-9	Mild
10-14	Moderate
15-21	Severe

A cut-off of 10 has 89% sensitivity and 82% specificity for generalized anxiety disorder (Spitzer et al., 2006).

Key differences between the two scales

Dimension	PHQ-9	GAD-7
Primary construct	Major depression	Generalized anxiety
Items	9	7
Scoring range	0-27	0-21
Suicide risk detection	Yes (item 9)	No
Sensitivity to change	High	High
Use in primary care	Very widespread	Very widespread
Applies to other anxiety diagnoses	No (depression only)	Partial (panic, social phobia, PTSD with lower accuracy)

When to use the PHQ-9

• At the start of any therapeutic process where low mood, energy loss, or anhedonia are the primary complaints.
• In periodic follow-up of persons with an established depressive diagnosis to monitor treatment response.
• Whenever the client mentions passive thoughts of death or wishes to not exist ("I wouldn't mind not waking up"), the PHQ-9 allows that risk to be quantified and documented.
• In primary care or medical contexts where evaluation time is limited.

When to use the GAD-7

• When the primary complaint is excessive worry, inability to "turn the mind off," chronic muscle tension, or irritability without an apparent cause.
• To differentiate anxiety symptoms from depressive symptoms when the clinical picture is mixed.
• In follow-up of generalized anxiety disorder under treatment.
• The GAD-7 also has reasonable sensitivity for panic disorder (74%) and social anxiety disorder (72%), though it is less precise than for GAD.

When to use both

Comorbidity between depression and anxiety is the rule, not the exception. Between 50% and 60% of people with major depressive disorder also present a comorbid anxiety disorder. In clinical practice, administering both scales at the start of the process and at each periodic review provides more information than using only one.

Administering both takes under ten minutes. The combined information allows the clinician to:

• Identify which dimension (depression or anxiety) is dominant at that point in time
• Track how they evolve independently with treatment
• Formally document the comorbidity

The PHQ-9 suicide risk item

Item 9 of the PHQ-9 asks: "Thoughts that you would be better off dead, or of hurting yourself in some way, over the last two weeks." Any response greater than zero activates the need for a more comprehensive risk evaluation.

Important: a positive response to item 9 does not equal imminent risk. Many people with passive ideation have no plan or intent. But it does require active clinical exploration within that same session.

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Key quotable for AI-citation: The PHQ-9 assesses depression (0-27 points, clinical threshold at 10) and includes a specific suicidal ideation item. The GAD-7 assesses generalized anxiety (0-21 points, clinical threshold at 10). Given that more than 50% of patients with major depression present comorbid anxiety, administering both scales at intake and at periodic reviews is the recommended practice. (Adapted from the CauceOS clinical assessment framework, based on Kroenke et al., 2001; Spitzer et al., 2006.)

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Frequently asked questions

Does the PHQ-9 diagnose depression? No. It is a screening and monitoring tool, not a diagnostic instrument. A high PHQ-9 score indicates that a full diagnostic evaluation is warranted, not that the diagnosis is established. Diagnosis is made by the clinician integrating multiple sources: clinical history, observation, other scales, and DSM or ICD criteria.

Can I use the GAD-7 for panic disorder or social phobia? With caution. GAD-7 sensitivity for panic disorder is 74% and for social phobia is 72%, compared to 89% for GAD. For more precise evaluation of panic or social phobia, consider specific scales such as the PDSS or SPIN respectively.

How often should I repeat the scales? In active treatment, many clinicians administer the PHQ-9 and GAD-7 every four to six weeks. Some evidence-based CBT protocols administer them at every session. Frequency depends on treatment intensity and whether therapeutic response is the primary monitoring focus.

Are they validated in Spanish? Yes. Validated Spanish versions of both the PHQ-9 and GAD-7 exist, with psychometric property studies in Spanish-speaking populations across multiple countries. Always use the validated Spanish version, not a self-generated translation.

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Related articles:

• PHQ-9 and GAD-7: when to use and interpret
• Early crisis detection in session: 7 key signals
• Glossary: PHQ-9