PHQ-9 accuracy Depression test
How accurate is the PHQ-9?
Short answer: the PHQ-9 is a well-validated screening tool — good at flagging who should have a fuller evaluation, not at handing out a diagnosis. It was developed by Kroenke, Spitzer & Williams in 2001 and has been tested against clinical interviews in independent studies. One of the most extensively validated depression screeners in the world, used across primary care and research.
Measured for major depression at a cutoff of 10 or higher.
What the numbers mean
Sensitivity is how often the test correctly flags people who do have the condition; specificity is how often it correctly clears those who don't. High figures on both mean the PHQ-9 misses few real cases while raising few false alarms — which is exactly what you want from a first-pass screen.
The honest limits
No screening tool is perfect, and self-administration online adds its own caveats:
- It measures symptoms over two weeks — a snapshot, not a lifelong picture.
- It cannot distinguish depression from grief, medical illness, or medication effects on its own.
- A score is not a diagnosis; only a clinician can make that call.
Does taking it online change the accuracy?
The questions and scoring here are identical to the clinical version, so the instrument itself is unchanged. What differs is context: a clinician also weighs your history, rules out other causes, and interprets borderline scores. That's why every result here points you toward a professional rather than standing in for one. Reproducing the instrument faithfully is our job; diagnosing is theirs.