Is a Patient Health Questionnaire-9 (PHQ9) score of 19 indicative of a depression diagnosis?

A PHQ-9 Score of 19 Does NOT Constitute a Depression Diagnosis

A PHQ-9 score of 19 indicates moderately severe to severe depressive symptomatology that requires further diagnostic assessment and immediate referral to psychiatry/psychology, but it is not itself a diagnosis of major depressive disorder. 1, 2

Understanding What the Score Means

• A PHQ-9 score of 19 falls in the range of 15-19, indicating moderately severe depressive symptomatology with significant functional impairment 1
• This score reflects symptom severity and functional impact, but screening tools alone cannot establish a psychiatric diagnosis 1, 2
• The PHQ-9 is a screening and severity measurement instrument, not a diagnostic tool—diagnosis requires meeting DSM-IV criteria through comprehensive clinical evaluation 2

Required Next Steps for PHQ-9 ≥15

For any PHQ-9 score ≥15, you must refer to psychology and/or psychiatry for formal diagnosis and treatment. 1

Before making a diagnosis, the following assessment is mandatory:

• Rule out medical causes first: Check thyroid function tests, complete metabolic panel, complete blood count, vitamin B12 and folate levels, and toxicology screen 1, 3
• Review all medications for mood-altering side effects, particularly interferon, corticosteroids, and beta-blockers 1, 3
• Assess for substance use or withdrawal that could explain symptoms 1
• Evaluate for delirium from infection or electrolyte imbalance, uncontrolled pain, or fatigue 2, 3

Diagnostic Criteria That Must Be Met

To diagnose major depressive disorder, the patient must meet specific DSM-IV criteria beyond just the PHQ-9 score:

• At least 5 of the 9 symptoms must be present during the same 2-week period 2
• At least one symptom must be either depressed mood or loss of interest/pleasure (anhedonia) 2
• Symptoms must cause clinically significant distress or functional impairment 2
• Medical and substance-induced causes must be ruled out before diagnosing a primary mood disorder 1, 2

Critical Safety Assessment

Immediately assess item 9 regarding self-harm thoughts—any positive response requires emergency psychiatric evaluation regardless of the total score. 1, 2, 3

• Never skip the suicidal ideation question, as omitting it artificially lowers scores and misses critical risk information 2, 3
• If any self-harm ideation is endorsed, refer for emergency evaluation immediately 2, 3

Common Pitfalls to Avoid

• Do not diagnose depression based on PHQ-9 score alone—this is a screening tool that identifies who needs diagnostic assessment 1, 2
• Do not fail to complete the full diagnostic assessment when PHQ-9 ≥8, which includes structured interview to confirm DSM-IV criteria 1
• Do not overlook medical causes—thyroid disorders, medication side effects, and metabolic abnormalities must be excluded first 1, 2, 3
• Do not underestimate severity—a score of 19 requires active specialist referral and treatment, not primary care management alone 1

Clinical Context

The PHQ-9 was validated as both a diagnostic aid and severity measure, with scores of 5,10,15, and 20 representing mild, moderate, moderately severe, and severe depression respectively 4. However, validation studies used structured mental health professional interviews as the criterion standard—the PHQ-9 identified who needed that diagnostic interview, it did not replace it 4. The tool demonstrates excellent sensitivity (88%) and specificity (88%) for major depression at a cutoff of ≥10, but this means it identifies probable cases requiring confirmation, not that it establishes diagnosis 4.