PHQ-9: What It Is, How It’s Used, and What the Research Shows

When a doctor asks you to fill out a short questionnaire about how you’ve been feeling, they might be using the PHQ-9, a nine-question screening tool used to identify depression symptoms in adults. Also known as the Patient Health Questionnaire-9, it’s one of the most widely used tools in primary care and mental health clinics across Canada and beyond. It’s not a diagnosis, but it gives providers a clear, consistent way to spot signs of depression early—before things get worse.

The PHQ-9 asks about common symptoms like low mood, loss of interest, trouble sleeping, fatigue, and even thoughts of self-harm. Each question is scored from 0 to 3, based on how often you’ve experienced it over the past two weeks. A total score of 10 or higher usually means moderate to severe depression and often triggers a follow-up. It’s quick—takes less than five minutes—and doesn’t need special training to use. That’s why clinics, urgent care centers, and even telehealth platforms rely on it. Studies from the Journal of General Internal Medicine show it’s just as accurate as longer interviews when it comes to catching depression in real-world settings.

What makes the PHQ-9 stand out is how it connects to real care. It doesn’t just label you—it guides next steps. A score of 5 might mean a check-in in a month. A score of 20? That often leads to a referral to a therapist or psychiatrist. It’s also used to track progress. If you’re on medication or therapy, your doctor might ask you to redo the PHQ-9 every few weeks to see if things are improving. This isn’t just paperwork—it’s a way to measure whether your treatment is working.

You’ll also find the PHQ-9 in research studies on antidepressants, telehealth outcomes, and even workplace mental health programs. It’s the baseline tool used to measure whether new treatments actually help people feel better. For example, studies comparing generic SSRIs to brand-name versions often use PHQ-9 scores to determine effectiveness. It’s the same tool used in Canada’s primary care networks to screen for depression during annual check-ups, especially for people with chronic illnesses like diabetes or heart disease, where depression often goes unnoticed.

It’s not perfect. Some people downplay their symptoms. Others don’t understand the questions. That’s why it’s always paired with a conversation—not just a number. But when used right, the PHQ-9 gives patients and providers a shared language. Instead of saying, "I’ve been feeling off," you can point to a score and say, "I’ve had little interest in things for most days this past month." That makes it easier to get help.

Below, you’ll find real stories and practical guides that tie into the PHQ-9’s role in care. From how antidepressants like paroxetine affect PHQ-9 scores, to how therapy and lifestyle changes help lower them over time, these posts show how this simple tool leads to real change. Whether you’re someone who took the test, a caregiver helping a loved one, or just curious about mental health screening, you’ll find useful, no-fluff insights here.