BMJ Research Reviews How Depression Scores Are Measured in Clinics

The BMJ has published research examining the minimal important difference — the smallest change in a patient’s score that actually means something in real life — for three depression screening tools: the Patient Health Questionnaire-9 (PHQ-9), the PHQ-8, and the shorter PHQ-2. These questionnaires are the most commonly used mental health outcome measures in clinical practice, according to the journal.

The PHQ-9 asks patients to rate nine symptoms of depression over the previous two weeks, producing a score that clinicians use to gauge severity and track whether a treatment is working. The PHQ-8 drops one item relating to self-harm, and the PHQ-2 covers just two core symptoms — making it a quick first-step screen. All three are used routinely across NHS services, including in Kent and Medway.

Knowing the minimal important difference matters because a score can shift between appointments without that change being meaningful to the patient’s day-to-day life. The BMJ research sets out to pin down where that threshold sits — so that clinicians, researchers, and patients can better judge whether a treatment has made a real difference, not just a statistical one.

The full findings are published in the BMJ.

If You’re Concerned About Your Mental Health

• Talk to your GP, who can carry out a depression screen and discuss next steps
• Call NHS 111 for advice if you’re unsure where to turn
• Samaritans are available 24 hours a day, seven days a week, on 116 123 — free from any phone