The Patient Health Questionnaire-9 (PHQ-9) Guide for Therapists

In Brief

The PHQ-9 ranks among the most widely used assessments in mental health care. It serves as a powerful tool for screening, diagnosing, and monitoring depression severity. Every mental health clinician should know how to administer and interpret the PHQ-9.

In this detailed guide, we'll explore the PHQ-9, its purpose, how to use it, and the insights it offers. We'll also look at the research supporting its validity and reliability, answer common questions, and suggest similar assessments to consider. Let's begin by addressing the fundamental question: What is the PHQ-9?

What is the Patient Health Questionnaire-9 (PHQ-9)?

‍The Patient Health Questionnaire-9 (PHQ-9) is a self-report assessment tool that screens for depression and measures its severity. It includes nine questions that align with the diagnostic criteria for major depressive disorder in the DSM-5.

What PHQ-9 measures

The PHQ-9 evaluates how often and how severely an individual experiences depressive symptoms over the past two weeks. It looks at the presence and extent of depressed mood, lack of interest or pleasure, mood, sleep disturbances, fatigue, appetite changes, feelings of worthlessness or guilt, concentration difficulties, psychomotor agitation or retardation, and suicidal thoughts. The PHQ-9 also captures the patient’s perception of how impactful the symptoms are on their daily functioning.

When do you use the Patient Health Questionnaire-9 (PHQ-9)?

‍The PHQ-9 serves many purposes in mental health care. Here are some key situations when you might use this assessment:

Associated focuses of treatment

Screening for Depression: The PHQ-9 primarily helps in identifying the presence and severity of depression in primary care and mental health settings.
Monitoring Treatment Progress: It can be given periodically to observe changes in depressive symptoms over time and evaluate the effectiveness of treatment interventions.

Age groups

Adults: The PHQ-9 is designed for use with adults aged 18 and older.
Adolescents: The PHQ-9 has been validated for use with adolescents ages 12-17; however a modified version of the measure, the PHQ-9 Modified for Teens, is also available for use with adolescents.

Associated diagnoses

Major Depressive Disorder: The PHQ-9 aligns with the diagnostic criteria for major depressive disorder in the DSM-5.
Other Depressive Disorders: It can also help in identifying other depressive disorders, such as persistent depressive disorder (dysthymia) and depressive disorder due to another medical condition.

Recommended frequency of use

Initial Assessment: Administer the PHQ-9 during the initial evaluation to establish a baseline measure of depression severity.
Follow-up Assessments: Re-administer the PHQ-9 at regular intervals, such as every 2-4 weeks or as clinically indicated, to track changes in depressive symptoms and treatment progress.
Discharge Planning: Use the PHQ-9 as part of the discharge planning process to evaluate the patient's readiness for discharge and inform aftercare recommendations.

What do you learn from the Patient Health Questionnaire-9 (PHQ-9)?

‍The PHQ-9 gives important insights into a person's experience with depression. Here's what you can understand from the scores and repeated use of this assessment:

Scores of PHQ-9 can let you know:

Depression Severity: The total score on the PHQ-9 shows the severity of depressive symptoms, ranging from minimal to severe. This assists in deciding the appropriate level of care and treatment approaches.
Specific Symptom Prevalence: The answers to individual questions highlight the presence and frequency of specific depressive symptoms, such as sleep disturbances, appetite changes, or suicidal thoughts. This information informs targeted interventions and risk assessment.
Diagnostic Considerations: While the PHQ-9 alone cannot diagnose depression, scores above certain thresholds suggest the need for further evaluation to determine if the individual meets the diagnostic criteria for major depressive disorder or another depressive disorder.
Functional Impairment: The PHQ-9 assesses the impact of depressive symptoms on the respondent’s daily life. This information can help establish and track medical necessity in clinical documentation when working with insurance companies.

What you can learn when PHQ-9 is given over time:

Treatment Progress: Comparing PHQ-9 scores across multiple administrations helps track changes in depressive symptoms over time. Decreases in scores indicate improvement, while increases or lack of change may signal the need to adjust treatment plans.
Relapse Prevention: Regularly using the PHQ-9, even after successful treatment, helps in spotting potential relapses early. Increases in scores can alert you to the need for timely intervention to prevent a full-blown depressive episode.
Long-Term Trends: Reviewing PHQ-9 scores over an extended period provides insights into a person's overall path of depressive symptoms. This information is useful for long-term treatment planning and assessing the effectiveness of ongoing interventions.

Research and Evidence behind the Patient Health Questionnaire-9 (PHQ-9)‍

History of PHQ-9 and who created it:

Developed by Robert L. Spitzer, Janet B.W. Williams, Kurt Kroenke, and colleagues in the late 1990s as part of the PRIME-MD (Primary Care Evaluation of Mental Disorders) diagnostic tool.
Adapted from the PRIME-MD Patient Health Questionnaire, which was a self-administered version of the PRIME-MD diagnostic instrument for common mental disorders.
Designed to be a concise, self-report tool for assessing and monitoring depression severity in primary care and mental health settings.

Strength of research and evidence behind PHQ-9:

Extensive validation studies across diverse populations and settings have demonstrated the PHQ-9's reliability, validity, and sensitivity to change.
High internal consistency with Cronbach's alpha ranging from 0.86 to 0.89 in primary care and obstetrics-gynecology clinics.
Excellent test-retest reliability with a correlation of 0.84 between administrations.
Strong construct validity, correlating significantly with other measures of depression severity, functional impairment, and quality of life.
Effective in detecting depression with a sensitivity of 88% and a specificity of 88% for major depression at a cutoff score of 10 or greater.

Limitations of PHQ-9:

Not a comprehensive diagnostic tool and should be used in conjunction with clinical judgment and other diagnostic methods.
May not capture all aspects of depression, particularly atypical or culture-specific presentations.
Potential for response bias, as it relies on self-report and may be influenced by factors such as social desirability or lack of insight.
Limited ability to differentiate between different types of depressive disorders, such as major depressive disorder and persistent depressive disorder (dysthymia).
May not be suitable for all populations, such as those with cognitive impairments or limited literacy skills.

Patient Health Questionnaire-9 (PHQ-9) Frequently Asked Questions (FAQ)

When should I use the PHQ-9?
The PHQ-9 works best for screening, diagnosing, and monitoring the severity of depression in adults and adolescents aged 12 and older. Many primary care and mental health settings use it during initial assessments, follow-up visits, and discharge planning.

How do I interpret the scores of the PHQ-9?
PHQ-9 scores range from 0 to 27, with higher scores indicating more severe depressive symptoms:

0-4: Minimal depression
5-9: Mild depression
10-14: Moderate depression
15-19: Moderately severe depression
20-27: Severe depression

Can the PHQ-9 diagnose depression on its own?
While the PHQ-9 serves as a useful tool for assessing depressive symptoms, it should not stand alone as the basis for a depression diagnosis. A comprehensive clinical evaluation, considering the individual's history, context, and other factors, is necessary for a proper diagnosis.

How often should I administer the PHQ-9?
The frequency of PHQ-9 administration depends on the clinical context and purpose:

Initial assessment: To establish a baseline measure of depression severity
Follow-up visits: Every 2-4 weeks or as clinically indicated to track changes and treatment progress
Discharge planning: To evaluate readiness for discharge and inform aftercare

Are there any limitations to using the PHQ-9?
Yes, the PHQ-9 has some limitations:

It relies on self-report and may be influenced by factors like social desirability or lack of insight
It may not capture all aspects of depression, particularly atypical or culture-specific presentations
It has limited ability to differentiate between different types of depressive disorders
It may not be suitable for individuals with cognitive impairments or limited literacy skills