PHQ-9 vs GAD-7: Depression and anxiety screening compared

Your doctor hands you a clipboard with two short questionnaires. One asks about sadness, energy, and sleep. The other asks about worry, tension, and fear. They look similar -- same response options, same two-week timeframe, even some of the same developers. So why are there two?

The PHQ-9 and GAD-7 are the two most widely used mental health screening tools in primary care. They were developed by overlapping research teams, use the same response format, and are often administered together. But they measure fundamentally different conditions, and understanding the distinction matters for both clinicians and the people filling them out.

The basics at a glance

Both instruments are free to use, take under three minutes, and share a clinical cutoff of 10. They were both developed with educational grants from Pfizer Inc. and published by the same core research team -- Drs. Kurt Kroenke, Robert Spitzer, and Janet Williams.

What each tool actually measures

The PHQ-9: Depression through nine lenses

The PHQ-9 maps directly onto the nine diagnostic criteria for major depressive disorder in the DSM. Each question targets a specific symptom:

1. Anhedonia: Loss of interest or pleasure in activities
2. Depressed mood: Feeling down, depressed, or hopeless
3. Sleep disruption: Trouble falling or staying asleep, or sleeping too much
4. Fatigue: Feeling tired or having little energy
5. Appetite changes: Poor appetite or overeating
6. Self-worth: Feeling bad about yourself or like a failure
7. Concentration: Trouble concentrating on things
8. Psychomotor changes: Moving or speaking noticeably slower or faster
9. Suicidal ideation: Thoughts of self-harm or being better off dead

This structure is deliberate. Because the items correspond to DSM criteria, the PHQ-9 can serve double duty: it screens for depression (using the total score) and provides a rough symptom profile (using individual item responses). A clinician can look at which items scored highest to understand the shape of a patient's depression.

The ninth item, suicidal ideation, carries special clinical weight. Any score above zero on this item triggers a safety assessment, regardless of the total score.

The GAD-7: Anxiety in seven dimensions

The GAD-7 targets the core features of generalized anxiety disorder:

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

While designed for generalized anxiety disorder specifically, the GAD-7 also detects other anxiety conditions. At a cutoff of 10, it shows 74% sensitivity for panic disorder, 72% for social anxiety disorder, and 66% for PTSD (Spitzer et al., 2006). It's a generalist anxiety tool, not a specialist one.

Items 2 and 3, uncontrollable worry about many things, are the signature features of GAD. High scores on these items in particular point toward generalized anxiety, while elevations on items 5 (restlessness) and 7 (apprehension/dread) may suggest panic or phobic elements.

Where they overlap -- and why it matters

Depression and anxiety are not separate islands. They co-occur frequently: roughly 50-60% of people with major depression also meet criteria for an anxiety disorder, and vice versa. This comorbidity is the rule, not the exception.

Both the PHQ-9 and GAD-7 touch on some shared territory:

- Sleep problems appear on the PHQ-9 (item 3) but not the GAD-7, even though insomnia is common in anxiety
- Concentration difficulties appear on the PHQ-9 (item 7) but are also characteristic of anxiety
- Restlessness appears on the GAD-7 (item 5) and overlaps with the PHQ-9's psychomotor item (item 8)
- Irritability appears on the GAD-7 (item 6) and is common in depression as well
- Fatigue is on the PHQ-9 (item 4) and frequently accompanies anxiety

This overlap means that someone with significant anxiety may score elevated on the PHQ-9 as well, and someone with depression may push their GAD-7 score into the moderate range. This is clinically useful information, not a flaw. It reflects the reality that these conditions share underlying mechanisms.

The correlation between PHQ-9 and GAD-7 scores typically ranges from r = 0.60 to 0.75 in clinical populations. High enough to show they're measuring related constructs, but distinct enough to provide unique information.

Psychometric comparison: How accurate are they?

Detecting their target conditions

Both tools perform well for their intended purpose:

The PHQ-9 has a slight edge in specificity (88% vs 82%), meaning it produces fewer false positives. The GAD-7 has marginally better sensitivity (89% vs 88%), meaning it's slightly better at not missing true cases. In practice, these differences are clinically negligible.

What the severity bands look like

PHQ-9 severity levels:

GAD-7 severity levels:

Notice that the PHQ-9 has five severity bands while the GAD-7 has four. The PHQ-9 splits its upper range into "moderately severe" and "severe," which can help guide treatment intensity. The GAD-7 combines these into a single "severe" category.

What counts as meaningful change

For both instruments, a 5-point change is considered clinically significant. If your patient's PHQ-9 drops from 18 to 12 over six weeks of treatment, that's meaningful progress. The same applies to the GAD-7.

For treatment response, a 50% reduction from baseline is the commonly used threshold. These benchmarks apply to both tools and make them practical for monitoring.

When to use each tool

Use the PHQ-9 when:

- Depression is the primary concern. The patient presents with low mood, loss of interest, fatigue, or sleep changes as primary complaints.
- You need to monitor depression treatment. The PHQ-9's five severity bands and established change thresholds make it ideal for tracking antidepressant or therapy response.
- You want diagnostic utility. Because the PHQ-9 maps to DSM criteria, it can support a provisional diagnosis using a diagnostic algorithm: if items 1 or 2 are endorsed at "more than half the days" and five or more total items meet that threshold, major depressive syndrome is likely.
- Suicidal ideation screening matters. Item 9 provides a built-in safety check that the GAD-7 doesn't offer.

Use the GAD-7 when:

- Anxiety is the primary concern. The patient reports excessive worry, tension, restlessness, or panic as their main issues.
- You want a broad anxiety screen. The GAD-7 picks up generalized anxiety, panic, social anxiety, and PTSD-related symptoms with reasonable sensitivity.
- The patient reports physical anxiety symptoms. Restlessness, difficulty relaxing, and feeling on edge are captured specifically by the GAD-7.
- You need a quick anxiety severity check. Seven items means even less patient burden than the PHQ-9's nine.

Use both when:

This is the most common clinical scenario, and for good reason.

- Routine screening in primary care. The USPSTF recommends depression screening for all adults. Adding the GAD-7 takes only 2-3 extra minutes and provides a much more complete picture. Together, the 16 items take about 5 minutes.
- The clinical picture is unclear. A patient who says "I just don't feel right" may have depression, anxiety, or both. Using both tools helps clarify what's driving the distress.
- Comorbidity is suspected. Since depression and anxiety co-occur in the majority of cases, screening for both is clinically responsible.
- Treatment monitoring for patients with both conditions. If someone is being treated for comorbid depression and anxiety, tracking both scores shows whether improvement is balanced or one condition is lagging.

Many health systems now use the PHQ-9 and GAD-7 together as a standard screening battery. Some even combine them into a single form.

A clinical decision flowchart

Here's a practical approach to using these tools together:

Step 1: Administer both the PHQ-9 and GAD-7.

Step 2: Evaluate the pattern.

- PHQ-9 >= 10, GAD-7 < 10: Depression is the primary concern. Focus assessment and treatment planning on depressive symptoms. Consider whether anxiety symptoms are subclinical or simply overshadowed.
- PHQ-9 < 10, GAD-7 >= 10: Anxiety is the primary concern. Evaluate for specific anxiety disorders (GAD, panic, social anxiety, PTSD). Consider whether depressive symptoms are emerging.
- Both >= 10: Comorbid depression and anxiety. This is common and usually requires integrated treatment. Both conditions should be addressed; treating only one often leaves the patient partially improved.
- Both < 10: No screening-level concern at present. If symptoms are reported despite low scores, consider whether the tools are capturing the patient's experience. Some specific anxiety disorders (OCD, specific phobias) are not well-detected by the GAD-7.

Step 3: Check critical items.

- PHQ-9 item 9 (suicidal ideation): Any endorsement requires safety assessment.
- GAD-7 items 2-3 (uncontrollable worry): High scores here point specifically toward generalized anxiety disorder.

Step 4: Consider the functional impact question.

Both tools include a supplementary question about how much these problems have affected work, home life, and relationships. This functional impairment item often provides the most clinically actionable data. Someone with moderate symptoms who is unable to work may need more aggressive intervention than someone with higher symptom scores who is still functioning.

For individuals: Understanding your own results

If you've taken both the PHQ-9 and GAD-7 on your own, here's how to interpret the combination:

Both scores under 5: Your depression and anxiety symptoms are in the minimal range. This is a reassuring baseline.

One or both scores 5-9: Some symptoms are present. Worth monitoring, especially if they've persisted for several weeks. Self-help strategies (exercise, sleep hygiene, stress management) are reasonable first steps.

One or both scores 10+: This is the level where professional input becomes important. Bring your results to your doctor or therapist. Having concrete numbers makes the conversation more productive.

PHQ-9 high, GAD-7 low (or vice versa): This pattern suggests one condition is more prominent. The dominant score tells you where to focus, but mention both to your provider, because the lower-scoring condition may still warrant attention.

Both scores high: You're likely experiencing both depression and anxiety. This is extremely common and doesn't mean you're somehow doubly broken. It means your provider has two clear targets for treatment, which is actually useful information.

Common questions about using both tools

Do I need to use both, or can I pick one?

If you can only choose one, pick the PHQ-9 for depression-focused settings and the GAD-7 for anxiety-focused settings. But using both takes less than 5 minutes combined and provides substantially more clinical information. Most guidelines recommend dual screening.

Can a high PHQ-9 score mean anxiety, not depression?

Partially. Because depression and anxiety share some symptoms (fatigue, sleep problems, concentration difficulties), a person with significant anxiety may score moderately on the PHQ-9 even without clinical depression. This is one reason using both tools is helpful; it helps untangle which symptoms belong where.

Can a high GAD-7 score mean depression, not anxiety?

Less commonly, but yes. Irritability (GAD-7 item 6) is a feature of depression, and restlessness can reflect agitated depression. Again, the combination of both scores provides the clearest picture.

My scores went in opposite directions during treatment. Is that normal?

It can be. Some treatments (particularly SSRIs) tend to improve anxiety before depression, or vice versa. CBT targeted at anxiety may improve GAD-7 scores while PHQ-9 scores lag. This isn't a treatment failure; it's useful information for adjusting the approach.

Are there populations where these tools don't work well?

Both have been validated across diverse populations, but performance may be reduced in settings with very low or very high prevalence of the target condition. Cultural factors can affect symptom reporting, and both tools focus on cognitive and emotional symptoms, which may underrepresent somatic presentations of depression or anxiety common in some cultural contexts.

The bigger picture: Why two short tools beat one long one

The power of the PHQ-9 and GAD-7 combination lies in its efficiency and specificity. In five minutes, you get:

- A calibrated depression severity score with established treatment thresholds
- A calibrated anxiety severity score with clinical cutoffs
- A suicidal ideation check
- Functional impairment data
- A baseline for monitoring treatment response over time

No single tool offers all of this. The DASS-21, for example, measures depression, anxiety, and stress in one 21-item instrument, but it wasn't designed for clinical screening and doesn't map to DSM criteria the way the PHQ-9 does. The PHQ-9 and GAD-7 together give you focused, clinically actionable data with minimal patient burden.

The bottom line

The PHQ-9 and GAD-7 are complementary tools, not competitors. The PHQ-9 is your depression screener: nine items, DSM-aligned, with a built-in suicidal ideation check. The GAD-7 is your anxiety screener: seven items, strong across multiple anxiety disorders, with excellent sensitivity.

Use the PHQ-9 when depression is the focus. Use the GAD-7 when anxiety is the focus. Use both when you want the most complete brief screening, which, in most clinical settings, is most of the time.

Five minutes. Sixteen questions. Two of the most well-validated scores in mental health. That's a remarkably good return on investment.