Assessment scales in psychology: PHQ-9, GAD-7 and good practice

Why use assessment scales?

Standardised assessment scales are structured questionnaires that help the psychologist put numbers on what a person is experiencing. Where a clinical interview explores depth and nuance, a scale adds a comparable, repeatable marker. The two are complementary: the scale never replaces clinical listening, it documents it.

In practice these tools serve two main purposes: screening — flagging the presence and intensity of symptoms that deserve attention — and follow-up — tracking how those symptoms change over the course of support. A crucial limit, stressed by health bodies, is that a scale does not make a diagnosis. It signals and quantifies; interpretation always belongs to the professional, in the person's overall context.

The PHQ-9: depressive symptoms

The PHQ-9 (Patient Health Questionnaire) is one of the most widely used questionnaires for depressive symptoms. Developed in the early 2000s by Kroenke, Spitzer and Williams, it is short, self-administered and freely available. The person rates how often various manifestations have occurred over a recent period, producing an overall score that reflects reported intensity and lends itself to follow-up.

The PHQ-9 also touches on suicidal ideation. A positive response there always calls for in-depth clinical exploration and, where there is risk, appropriate referral — a clear reminder that a scale is never read mechanically.

The GAD-7: anxiety

The GAD-7 (Generalized Anxiety Disorder) is the counterpart for anxiety. Developed a few years later by the same team, it explores the frequency of anxiety-related manifestations over a recent period and likewise yields an overall intensity score. Short and well studied, it is often used alongside the PHQ-9, since anxiety and depressive symptoms frequently coexist. As with the PHQ-9, the score is only an indicator, not a diagnosis.

| | PHQ-9 | GAD-7 | |---|---|---| | Domain | Depressive symptoms | Anxiety manifestations | | Format | Short self-report | Short self-report | | Main use | Screening and follow-up | Screening and follow-up | | Output | Overall intensity score | Overall intensity score |

The value of longitudinal follow-up

This is perhaps where the scales prove most useful. Completing a questionnaire once gives a snapshot; repeating it at regular intervals gives a moving picture. The trend in the score — falling, stable or rising — becomes a concrete basis for objectifying progress and sharing it with the person, spotting a deterioration that warrants adjusting care, and feeding clinical reflection. This requires keeping a secure, ordered history of administrations, so a scattered series of numbers becomes a genuine curve.

Limits and precautions: a tool, not a diagnosis

Scales are useful provided their limits are understood:

• They do not diagnose. A high score signals intensity of symptoms, not a disease; only clinical judgement, in context, allows valid interpretation.
• They are self-reported. Answers depend on understanding, current state, culture and trust. The same score can cover different realities.
• Context matters. Life situation, history and recent events are things the interview explores and the scale does not.
• Safety first. Faced with suicidal ideation or a crisis, the priority is not to calculate a score but to ensure the person's safety and refer without delay to the appropriate emergency or crisis services in their country.

Other well-known instruments exist, such as the BDI (Beck Depression Inventory) for depressive symptoms or the MMSE (Mini-Mental State Examination) for cognitive screening — each with its own domain and limits.

Key takeaway

Assessment scales such as the PHQ-9 (depressive symptoms) and GAD-7 (anxiety) are valuable markers for screening and following symptom intensity, especially when repeated over time. They never replace clinical evaluation or the practitioner's judgement, and any crisis calls for referral to emergency services. For psychologists, Cabdivin supports this work with structured records, a dated history of administrations and progress tracking in a privacy-respecting tool. Free 14-day trial, no credit card required — see the offer for psychologists.