What is the recommended course of action for a patient with depressive symptoms based on their Patient Health Questionnaire-9 (PHQ-9) rating scale results?

PHQ-9 Score Interpretation and Management Algorithm

The PHQ-9 score determines your treatment pathway: scores 1-7 require no intervention, scores 8-14 mandate low-intensity interventions (guided self-help CBT, structured exercise, or pharmacotherapy), scores 15-19 require immediate referral to psychology/psychiatry for high-intensity therapy, and scores 20-27 demand urgent psychiatric intervention. 1, 2, 3

Immediate Safety Assessment (Overrides All Score-Based Decisions)

• If item 9 (self-harm thoughts) is endorsed at any level, immediately refer for emergency psychiatric evaluation regardless of total PHQ-9 score. 1, 2, 3
• Never omit item 9 from your assessment—this artificially lowers scores and misses life-threatening risk. 1, 2, 3
• The frequency and specificity of self-harm thoughts are the most critical factors for risk stratification. 1, 2
• Facilitate one-to-one observation if self-harm risk is present. 1

Score Interpretation and Clinical Significance

Minimal Depression (PHQ-9: 1-7)

• Patients typically have effective coping skills and adequate social support. 2
• No active intervention required; routine follow-up is sufficient. 2

Moderate Depression (PHQ-9: 8-14)

• This represents clinically significant depression requiring active treatment, not watchful waiting. 1, 2, 3
• Symptoms interfere with work, relationships, and daily activities with mild to moderate functional impairment. 1, 2
• May not meet full DSM-IV criteria for major depressive disorder but still requires intervention. 1

Moderately Severe Depression (PHQ-9: 15-19)

• Symptoms interfere moderately to markedly with functioning. 2
• Immediate referral to psychology and/or psychiatry for formal diagnosis and treatment is mandatory. 2, 3

Severe Depression (PHQ-9: 20-27)

• Significant functional impairment is present requiring urgent intervention. 2
• Immediate psychiatric referral is required. 2, 3

Diagnostic Workup Before Treatment Initiation

Rule Out Medical and Substance-Induced Causes

• Check thyroid function (TSH, free T4), complete metabolic panel, complete blood count, vitamin B12, and folate levels. 1, 3
• Review medications for mood-altering side effects: interferon, corticosteroids, beta-blockers. 4, 1, 3
• Assess for uncontrolled pain, fatigue, and delirium. 3

Obtain Pertinent History

• Prior mood disorders, comorbid anxiety disorders, substance use history, and chronic medical illnesses. 1
• Duration of symptoms, sociodemographic risk factors (unemployment, low financial resources, living alone, lower education level). 1
• Degree of functional impairment in work, relationships, and daily activities. 1

Treatment Algorithm Based on PHQ-9 Score

For Scores 8-14 (Moderate Depression)

• Initiate low-intensity interventions: 1, 2, 3
  • Individually guided self-help based on cognitive behavioral therapy (CBT) with behavioral activation and problem-solving. 1, 2
  • Structured physical activity programs. 1, 2
  • Psychosocial group interventions led by licensed mental health professionals covering stress reduction, positive coping strategies, enhancing social support, and health behavior change. 1
• Consider pharmacologic treatment based on clinical judgment and patient preference. 1, 3
• Make referral to psychology or psychiatry for determination of formal diagnosis. 1

For Scores 15-27 (Moderately Severe to Severe Depression)

• Immediate referral to psychology and/or psychiatry is mandatory. 2, 3
• High-intensity interventions delivered by licensed mental health professionals are required, including: 2
  • Individual psychological therapy using treatment manuals that incorporate cognitive change, behavioral activation, and biobehavioral strategies. 2

Monitoring and Follow-Up

• Reassess with PHQ-9 at regular intervals during treatment to monitor treatment response. 1, 3
• Administer PHQ-9 at initial diagnosis, regular intervals during treatment, and at 3,6, and 12 months after treatment completion. 2
• A change of 5 points on the PHQ-9 scale represents the minimal clinically important difference for individual patient improvement. 5

Critical Pitfalls to Avoid

• Do not use watchful waiting for scores ≥8—this represents clinically significant depression requiring active treatment, not observation alone. 1, 3
• Never fail to complete the full 9-item PHQ-9 if you administered only the initial 2-item screen (anhedonia and depressed mood questions). 1, 2
• Do not overlook medical causes of depression before diagnosing a primary mood disorder. 1, 3
• Never skip item 9 on self-harm—this is the most dangerous omission. 3

Special Population Considerations

Elderly Patients

• Consider using the Geriatric Depression Scale (GDS-15) instead of PHQ-9, which focuses on affective symptoms and excludes somatic items confounded by medical illness. 2, 3

Patients with Cognitive Impairment

• The PHQ-9 loses accuracy in this population; use alternative assessment methods such as informant-based tools. 2, 3

Cultural Considerations

• Use culturally sensitive assessments when possible and tailor evaluation for patients with learning disabilities. 1, 2

Screening Approach for Efficiency

• Use a two-step approach: initially screen with the first 2 PHQ-9 items (anhedonia and depressed mood). 2, 3
• Complete the full 9-item questionnaire only if either item scores ≥2. 2, 3
• If both items score 0-1, the screen is negative and no further assessment is needed. 2