From Data to Diagnosis: Monitoring Depression with the PHQ-9

By Proud Ua-arak

Mental health is just as important as physical health, yet many people struggle to recognize when they need support. Depression, one of the most common mental health conditions, often goes undiagnosed because its symptoms can be subtle or mistaken for everyday stress. That’s where mental health screening tools like the PHQ-9 (Patient Health Questionnaire-9) come in. Designed to assess and track symptoms of depression, the PHQ-9 provides a simple way to check in on your mental well-being. In this post, we’ll explore how the PHQ-9 works, why it matters, its limitations, and how it can help you navigate your mental health.

Marketing: How it All Started

Since the PHQ-9 is a widely-used, validated mental health screening tool, you might be surprised to know that it started not as a clinical breakthrough, but rather as a clever marketing move. Around 30 years ago, Pfizer funded the development of the PHQ-9 to simplify screening for depression, with the added benefit of encouraging more primary care providers to prescribe Zoloft, now one of the most common antidepressants used today. In comparison to other depression screening tools at the time, the PHQ-9 stood out due to its relative shortness and ease of administration compared to the Hamilton Depression Rating Scale (HAM-D), which takes 15-30 minutes and is typically administered by a clinician. Additionally, the PHQ-9 reflected the diagnostic criteria of Major Depressive Disorder per the DSM-IV at the time, unlike other short self-report tools.

The PHQ-9: A Short and Sweet Mental Health Check-In Tool

The PHQ-9 is a simple 9-question survey that assesses the presence and severity of symptoms of depression over the past two weeks. It asks about the frequency of the following: loss of interest in activities (anhedonia), feeling down or depressed, changes in sleep, energy levels, appetite, guilt, concentration, motor changes, and thoughts of suicide. By looking at a two-week period, it avoids emphasizing the ups and downs of a single bad or good day, making results more reliable. A higher score indicates more severe depression, and clinicians sometimes use the scores to help determine further treatment recommendations. 

The PHQ-9 isn’t meant to replace a full mental health evaluation, nor is it a one-time assessment. It starts with a first check-in to get a baseline of how you’re feeling. Then, follow-up check-ins (no more than once every two weeks) can help keep an eye on any changes. 

One common use case is to monitor the severity of depression over time to assess how well certain treatments like medications are working, giving both individuals and clinicians valuable insight. Follow-ups can show what’s working and what might need tweaking. Using the PHQ-9 this way makes it easier to spot patterns, track progress, and take steps toward feeling better. 

What Are the Limitations of the PHQ-9?

Although the PHQ-9 does a great job of reflecting the psychiatric diagnostic criteria for major depressive disorder (MDD), it does not paint a full picture of how depression manifests. Depression takes on many shapes and forms beyond MDD; it is important to distinguish between the kinds of depression, such as major depressive disorder, seasonal affective disorder, and depression associated with bipolar disorder. Clinicians may track outcomes data using the PHQ-9 scores, although patients may have different goals in life. It’s important to tell your clinician what matters most for you – what are you hoping to get out of treatment?

Why We Ask

A 9-question survey certainly does not fully capture the intricacies of individual mental health, so why take it in the first place? Regardless of its shortcomings, the PHQ-9 is useful in gauging a general understanding of your mental health status, tracking progress, and identifying symptoms before they worsen. 

At Lucid Care, we believe that just a bit of data to track progress can go a long way. We use the PHQ-9 as part of a bigger approach, combining data, clinical support, and self-care tools to help people take charge of their mental well-being. Ultimately, we believe in a holistic overview that empowers people to feel capable and in control of their mental health journey. 

Sources

Goldhill, O. (2023, February 21). How a depression test devised by a Zoloft marketer became a crutch for a failing mental health system. STAT. https://www.statnews.com/2023/02/21/depression-test-phq9-zoloft-pfizer-mental-health/ 

Kroenke, K., Spitzer, R. L., & Williams, J. B. (2001). The PHQ-9: validity of a brief depression severity measure. Journal of general internal medicine, 16(9), 606–613. https://doi.org/10.1046/j.1525-1497.2001.016009606.x

MDCalc: PHQ-9