PHQ-9: How We Measure Whether Treatment Is Actually Working

If you have spent years in treatment for depression, you have probably answered the question a hundred times: "How are you feeling?" It is a good question, but it is a slippery one. On a rough week, feelings can color everything darker than the facts warrant. On a hopeful week, you might round yourself up to "fine" because you want it to be true. That is exactly why, at every visit, we do something that looks almost clinical in its simplicity. We ask you to fill out a short questionnaire and we write down a number. This article is about that number, what it is, why we trust it, and how phq-9 depression measurement helps us tell the difference between real progress and wishful thinking.

What the PHQ-9 actually is

The PHQ-9 is a nine-question survey. It asks, over the last two weeks, how often you have been bothered by things like low mood, loss of interest, trouble sleeping, low energy, poor appetite, difficulty concentrating, and thoughts that you would be better off not here. Each item is scored from 0 ("not at all") to 3 ("nearly every day"), so your total lands somewhere between 0 and 27. Higher means more symptom burden. It takes about two minutes, and you fill it out yourself.

What makes it useful is not that it is fancy, because it is not. What makes it useful is that it is the same nine questions, scored the same way, every single time. That consistency turns something invisible and hard to describe into something we can actually follow across weeks and months. When we talk about phq-9 depression measurement, we are really talking about giving you and your clinician a shared, honest ruler.

Why a number, and not just a feeling

Feelings are real and they matter. But they are also easy to misremember. Ask most people how they slept last month and they will shrug. Ask them their PHQ-9 from four visits ago and we can pull the exact figure. A tracked number does a few things a feeling cannot:

• It catches slow, quiet improvement you might not notice day to day, the kind that only shows up when you compare a 19 in March to a 12 in May.
• It flags when something is not working, so we are not politely waiting six more months on a plan that has stalled.
• It gives specific items, like sleep or concentration, that we can watch on their own, since depression does not lift all at once or evenly.
• It keeps everyone honest, including us. The number does not care how much anyone wants the treatment to be working.

The point is not to reduce you to a score. The point is to make sure that when we say something is helping, we can show you why we believe it, and when it is not, we can see that early and change course.

When the number will not move, and why that matters

Sometimes the number stays stubbornly high no matter what is tried. Someone works through several antidepressants, does the therapy, keeps every appointment, and the PHQ-9 barely budges. When that happens, it is worth asking a different question than "which medication next." It is worth asking whether this depression is running on a system that standard antidepressants are simply not built to reach.

Here is where history matters. If you ever got your bell rung - a hard hit in sports, a car accident, a fall, a blast, a fight - that old event can quietly raise your risk of depression years or even decades later. People with a bell-ringing hit are more than three times as likely to experience depression, and that elevated risk persists for years (Beaton et al., 2020, Frontiers in Neurology). This does not mean an old hit caused everything, and it is a risk factor, not a diagnosis. But it can help explain why the usual playbook kept coming up short.

There is a mechanical reason for the mismatch. Most common antidepressants work on serotonin. But the kind of depression that can follow a hit may run more on a different system, glutamate. In one meta-analysis, antidepressants started after a head impact showed no significant difference from placebo (Foreman et al., 2019, J Head Trauma Rehabil). That is not a knock on those medicines. It is a clue that in some people the target was in a different place all along.

The role of neurology, and a different mechanism

This is why we keep neurology on staff. Neurology is a diagnostic lens, a way to look carefully at your history and ask why standard care may have missed the mark. It is not a promise of any particular outcome. It is simply a more complete way of understanding what you are dealing with, especially when an old head injury sits somewhere in your story alongside things like ongoing sleep trouble, which affects a large share of people with a head-injury history.

Ketamine and esketamine act on that other system, glutamate, rather than serotonin. Their effects can be measurable in hours, and researchers describe a roughly 24 to 72 hour window of heightened neuroplasticity afterward (Zanos and Gould, 2018, Molecular Psychiatry). To be clear about what this is and is not: Spravato (esketamine) is FDA-approved for treatment-resistant depression. It is not approved for concussion or any head injury, and an old hit is a risk factor for hard-to-treat depression, never by itself a reason to use ketamine. What ties all of this back to the beginning is measurement. Whichever path someone is on, the PHQ-9 at every visit is how we tell whether it is genuinely helping.

What this means for you

If you have been carrying a low mood that no one has been able to move, and somewhere back in your history you took a real hit, those two facts may be more connected than anyone has told you. That is not a reason for alarm. It is a reason for a closer look. A proper evaluation from a clinic that has neurology on staff can consider whether an old head injury belongs in the picture, and then we can watch the number, visit by visit, to see what actually helps.

One last, important note. The PHQ-9 includes a question about thoughts of being better off gone, and we read that item carefully every time, because a concussion history is associated with elevated odds of death by suicide (Erlangsen et al., 2018, JAMA). If you are having those thoughts right now, you deserve support today - you can call or text 988 in the United States to reach the Suicide and Crisis Lifeline, any hour. You do not have to sort this out alone, and understanding what you are up against is the first calm step toward getting the right kind of help.