How is depression treatment guided by Patient Health Questionnaire-9 (PHQ-9) scores?

PHQ-9 Guided Depression Treatment

Depression treatment should be guided by PHQ-9 scores using a cutoff of 8 or higher for clinically significant depression, with treatment intensity escalating based on score ranges: scores 8-14 warrant low-intensity interventions like guided self-help or structured physical activity, while scores 15 or higher require immediate referral to psychology/psychiatry for high-intensity interventions delivered by licensed mental health professionals. 1, 2

Phased Screening Approach

Initial Two-Item Screen:

• Begin with the first two PHQ-9 items assessing anhedonia ("Little interest or pleasure in doing things") and depressed mood ("Feeling down, depressed or helpless") 1, 2
• If either item scores 2 or higher (occurring "more than half the days" or "nearly every day"), complete the full 9-item PHQ-9 1, 2
• If both items score 0-1, no further screening is needed 1, 2
• This approach reduces the number of patients needing full assessment by approximately 57% 3

Score Interpretation and Treatment Algorithm

Minimal Symptoms (PHQ-9: 1-7):

• No or minimal symptoms of depression with effective coping skills and social support 1, 2
• No active intervention required beyond routine monitoring 1, 2

Moderate Depression (PHQ-9: 8-14):

• Subthreshold depressive symptoms with mild to moderate functional impairment 1, 2
• Seek consultation with psychology or psychiatry for diagnostic confirmation 1
• Initiate low-intensity interventions including: 2, 4
  • Individually guided self-help based on cognitive behavioral therapy (CBT) with behavioral activation and problem-solving 2, 4
  • Structured physical activity programs 2, 4
  • Consider pharmacologic treatment as appropriate 2

Moderate to Severe Depression (PHQ-9: 15-19):

• Most depressive symptoms present with moderate to marked functional interference 1, 2
• Mandatory referral to psychology and/or psychiatry for formal diagnosis and treatment 1, 2
• High-intensity interventions delivered by licensed mental health professionals using treatment manuals that incorporate cognitive change, behavioral activation, and biobehavioral strategies 2

Severe Depression (PHQ-9: 20-27):

• Severe symptomatology with significant functional impairment 2, 5
• Immediate referral to psychology and/or psychiatry required 2, 5
• High-intensity interventions with close monitoring 2

Critical Safety Assessment

Self-Harm Evaluation (Item 9):

• Never omit item 9 regarding thoughts of self-harm, as this artificially lowers scores and misses critical risk information 1, 2
• If any self-harm ideation is endorsed, immediate referral for emergency psychiatric evaluation is mandatory regardless of total PHQ-9 score 1, 2, 4
• Facilitate safe environment with one-to-one observation and initiate interventions to reduce risk of harm 1, 4
• The frequency and specificity of self-harm thoughts are most important for risk assessment 1, 5
• Individuals typically do not endorse self-harm exclusively but rather with several other symptom endorsements 1

Comprehensive Clinical Assessment

Before initiating treatment, evaluate: 1, 2, 5

• Duration of depressive symptoms 1, 2
• Associated sociodemographic factors 1, 2, 4
• Psychiatric or health comorbidities 1, 2, 4
• Social impairments and functional impact 1, 2
• Medical causes including thyroid disorders, electrolyte imbalances, medication side effects, and substance use 5

Monitoring Treatment Response

Follow-up Assessment Timing:

• Administer PHQ-9 at initial diagnosis/start of treatment 2
• Regular intervals during treatment 1, 2
• At 3,6, and 12 months after treatment completion 1, 2
• During times of personal transition, family crisis, or disease progression 1, 2
• When approaching end of life in palliative care settings 2

Treatment Response Indicators:

• A clinically meaningful change is 5 points on the PHQ-9 scale 6
• At Week 4 of treatment, PHQ-9 ≥17 predicts poor response and may warrant treatment intensification 7
• At Week 9, PHQ-9 ≥13 suggests inadequate response 7
• At Week 14, PHQ-9 ≥9 indicates continued need for intervention 7

Common Pitfalls to Avoid

• Do not underestimate moderate scores (8-14)—these represent clinically significant depression requiring active treatment, not "watchful waiting" 2, 4
• Do not fail to complete the full PHQ-9 when initial two-item screening suggests depression 2, 5, 4
• Do not rely solely on symptom count without assessing functional impairment 1, 5
• Do not overlook medical or substance-induced causes before diagnosing primary depression 5

Special Population Considerations

Modified Assessment Approaches:

• Use culturally sensitive assessments when possible 1, 2
• Tailor evaluation for patients with learning disabilities or cognitive impairments 2, 5
• The PHQ-9 loses accuracy in patients with cognitive impairment; consider alternative tools like the Geriatric Depression Scale (GDS) for elderly patients with cutoffs ≥19 for GDS-30 or ≥5 for GDS-SF-15 5
• For cancer or medically ill patients, consider the Hospital Anxiety and Depression Scale (HADS) which excludes somatic symptoms that may be confounded by medical illness, with scores ≥8 indicating caseness 5