What is the approach to diagnosing depression in a patient?

Diagnosis of Depression

Initial Screening Approach

Begin by asking two simple screening questions: "Over the past 2 weeks, have you felt down, depressed, or hopeless?" and "Over the past 2 weeks, have you felt little interest or pleasure in doing things?" These questions are as effective as longer formal instruments for initial screening 1.

• If the patient answers "no" or minimally to both questions, no further screening is needed at this time 1.
• If the patient endorses either question, proceed immediately to full assessment with the PHQ-9 1, 2.

Immediate Safety Assessment

Before proceeding with diagnostic evaluation, assess for imminent safety concerns that require emergency intervention:

• Ask directly about suicidal ideation: "Have you had thoughts of hurting yourself or that you would be better off dead?" 2.
• Evaluate for risk of harm to self or others, severe agitation, psychosis, or confusion—any of these require immediate psychiatric or emergency referral 2.
• If any safety concerns are present, facilitate emergency evaluation by a licensed mental health professional and ensure a safe environment with one-to-one observation 1, 2.

Structured Assessment with PHQ-9

Administer the full 9-item Patient Health Questionnaire (PHQ-9) to quantify symptom severity:

• The PHQ-9 directly maps to DSM criteria and provides standardized scoring from 0-27 2, 3.
• Score interpretation: 1-7 (minimal symptoms), 8-14 (moderate symptoms), 15-19 (moderate to severe symptoms), 20-27 (severe symptoms) 1, 2.
• Patients scoring ≥15 require immediate referral to psychiatry or psychology for diagnosis and treatment 2, 4.
• Patients scoring 8-14 need consultation with mental health professionals for diagnostic determination 1.

Critical Caveat About Item 9

• Item 9 of the PHQ-9 specifically assesses thoughts of self-harm 1, 2.
• If this item is endorsed at any frequency, immediate safety evaluation is mandatory regardless of total score 1, 4.
• Do not omit this item from screening, as doing so artificially lowers the score and may miss patients at risk 1.

Formal Diagnostic Confirmation

All positive screening results must be followed by a full diagnostic interview using DSM-5 criteria—screening tools alone do not establish a diagnosis 1, 2.

DSM-5 Criteria for Major Depressive Disorder

To confirm MDD, the patient must have:

• At least 5 of 9 symptoms present for at least 2 weeks 3.
• At least one symptom must be either depressed mood or anhedonia (loss of interest/pleasure) 3.
• The 9 symptoms are: depressed mood, anhedonia, appetite/weight change, sleep disturbance, psychomotor agitation or retardation, fatigue, feelings of worthlessness or guilt, concentration difficulties, and recurrent thoughts of death or suicidal ideation 3, 5.
• Symptoms must cause clinically significant distress or impairment in social, occupational, or other important functioning 3.

Essential Exclusion Questions

• Ask about periods of elevated mood, increased energy, or decreased need for sleep lasting several days to exclude bipolar disorder 3.
• Screen for active substance use disorder by asking about regular use of alcohol, drugs, or other substances 3.
• Assess whether symptoms are better explained by bereavement, medical illness, or medications 1.

Assessment of Functional Impairment and Comorbidities

Evaluate how symptoms impact specific life domains:

• Assess work performance, relationships with family and friends, and social activities 3.
• Screen for comorbid anxiety using the GAD-7 scale (scores of 5,10, and 15 indicate mild, moderate, and severe anxiety respectively) 2.
• Evaluate for substance use disorders, panic attacks, and other psychiatric comorbidities 1.

Risk Factor Assessment

Identify patients at higher risk who warrant closer monitoring:

• Previous personal or family history of depression, bipolar disorder, or suicide-related behaviors 2.
• Other psychiatric disorders including substance misuse 1.
• Chronic medical diseases (cardiovascular, cancer, metabolic, inflammatory, neurological disorders) 1, 6.
• Unemployment or lower socioeconomic status 1.
• Women have higher risk than men 1.
• In older adults, consider medical illness, cognitive decline, bereavement, and institutional placement 1.

Special Population Considerations

Tailor assessment approaches for specific populations:

• Use culturally sensitive assessments and consider language barriers 1.
• For older adults, use the Geriatric Depression Scale as an alternative screening tool 7.
• For patients with cognitive impairment, interview family members or caregivers for collateral information 2.
• Be aware that depression in older adults can be difficult to detect due to atypical presentations 1.

Common Diagnostic Pitfalls to Avoid

• Do not rely solely on screening scores—always conduct a clinical interview to confirm diagnosis 2, 3.
• Do not dismiss somatic symptoms (fatigue, pain, sleep disturbance) as purely medical—these are common presentations of depression 8, 9.
• Do not fail to screen for bipolar disorder before initiating antidepressant treatment, as antidepressants alone may precipitate manic episodes 5.
• Do not overlook the need for adequate follow-up systems—screening without treatment infrastructure provides minimal benefit 1, 7.

Documentation Requirements

Document the following elements:

• Duration of symptoms (must be at least 2 weeks) 3.
• Specific symptoms present and their frequency 3.
• Degree of functional impairment in multiple domains 3.
• Assessment of suicide risk 2.
• Presence or absence of exclusionary conditions (bipolar disorder, substance use, medical causes) 3.
• Previous episodes of depression to assess for recurrent pattern 3.