What are the diagnostic criteria for Major Depressive Disorder (MDD)?

How to Diagnose Major Depressive Disorder

Diagnose MDD by applying DSM-5 criteria through direct clinical interview: the patient must have at least 5 of 9 specific symptoms present during the same 2-week period, with at least one symptom being either depressed mood or loss of interest/pleasure (anhedonia), and these symptoms must cause significant functional impairment. 1, 2

Core Diagnostic Requirements

The diagnosis requires meeting all of the following:

• At least 5 symptoms from the DSM-5 list present during the same 2-week period 2
• At least one symptom must be either:
  • Depressed mood (or irritability in adolescents), OR
  • Anhedonia (loss of interest or pleasure in activities) 1, 2
• Symptoms must cause clinically significant distress or impairment in social, occupational, or other important areas of functioning 1

The 9 DSM-5 Symptom Criteria to Assess

Systematically evaluate for these specific symptoms 2:

1. Depressed mood most of the day, nearly every day (in adolescents, may present as irritability) 1
2. Anhedonia - markedly diminished interest or pleasure in all or almost all activities 2
3. Weight/appetite changes - significant weight loss or gain, or decrease/increase in appetite 2
4. Sleep disturbance - insomnia or hypersomnia nearly every day 1, 2
5. Psychomotor changes - agitation or retardation observable by others 1, 2
6. Fatigue or loss of energy nearly every day 1, 2
7. Feelings of worthlessness or excessive/inappropriate guilt 2
8. Diminished concentration or indecisiveness nearly every day 2
9. Recurrent thoughts of death or suicidal ideation 2

Diagnostic Process Algorithm

Step 1: Use Standardized Screening Tools

• Administer the Patient Health Questionnaire-9 (PHQ-9) as an initial screening instrument 2, 3
• A positive screen (elevated score) does NOT equal a diagnosis but triggers comprehensive assessment 1
• Screen even if the patient doesn't explicitly report depression, particularly if presenting with somatic complaints, family conflict, academic decline, or other emotional problems 1

Step 2: Conduct Direct Clinical Interview

• Perform face-to-face interview with the patient - standardized tools aid but do not replace clinical interview 1
• Interview family members or caregivers separately to obtain collateral information 1
• Probe specifically for each of the 9 DSM-5 symptoms listed above 1
• Assess duration (must be at least 2 weeks) and persistence (nearly every day) 2

Step 3: Assess Functional Impairment

• Evaluate impairment across multiple domains: home, school/work, peer relationships, and social functioning 1
• Document subjective distress reported by the patient 1
• Use the Sheehan Disability Scale to quantify functional impairment 1

Step 4: Rule Out Other Conditions

• Exclude bipolar disorder - screen for history of manic or hypomanic episodes 1
• Assess for substance-induced mood disorder - determine if symptoms are due to substance use or withdrawal 1
• Evaluate for depression due to medical condition - consider thyroid disease, neurological conditions, medications 4
• Screen for comorbid psychiatric conditions: anxiety disorders, PTSD, personality disorders 1

Step 5: Conduct Safety Assessment

• Immediately assess for suicidal ideation, plan, intent, and recent attempts - this is mandatory regardless of diagnosis 1, 3
• Patients with specific suicide plan, clear intent, recent attempt, or psychotic symptoms should be classified as severe regardless of symptom count 1

Severity Classification

Once MDD is diagnosed, classify severity 1:

• Mild: 5-6 symptoms of mild intensity with minimal functional impairment 1
• Moderate: Symptom severity and functional impairment between mild and severe 1
• Severe: All 9 symptoms present, OR severe functional impairment (unable to leave home), OR presence of suicidal plan/intent/recent attempt, OR psychotic features 1

Assessment Tools for Severity Monitoring

After diagnosis, use these instruments to track severity and treatment response 2:

• Montgomery-Åsberg Depression Rating Scale (MADRS) - clinician-administered, focuses on core depressive symptoms 1, 2
• Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR) - patient-reported outcome measure 1, 2
• Hamilton Depression Rating Scale (HAM-D) - alternative clinician-administered scale 2

Common Diagnostic Pitfalls

• Don't rely solely on screening tool scores - a positive PHQ-9 requires full diagnostic assessment via clinical interview 1
• Don't miss atypical presentations - adolescents may present with irritability rather than sadness, and somatic complaints (fatigue, pain, sleep problems) may be the chief complaint 1
• Don't overlook functional impairment - symptom count alone is insufficient; document how symptoms affect daily functioning 1
• Don't skip the safety assessment - suicidality must be evaluated in every patient with suspected depression 1
• Don't miss comorbidities - assess for anxiety, substance use, and other psychiatric conditions that commonly co-occur and affect treatment 1
• Don't diagnose MDD if symptoms are better explained by bipolar disorder - always screen for manic/hypomanic episodes 1