What is the recommended approach for an initial psychiatric evaluation for a patient with depression?

Initial Psychiatric Evaluation for Depression

The initial psychiatric evaluation for depression should focus on establishing DSM/ICD criteria through a structured clinical interview that assesses the nine core symptoms of major depression, duration, functional impairment, and excludes medical causes and other psychiatric conditions, with standardized screening questionnaires serving as adjuncts rather than diagnostic tools.

Core Diagnostic Approach

Symptom Assessment

• Directly assess the nine DSM criteria for major depression through clinical interview: depressed mood, anhedonia, weight/appetite changes, sleep disturbance, psychomotor changes, fatigue, worthlessness/guilt, concentration difficulties, and suicidal ideation 1
• Recognize that depression frequently presents with physical symptoms as the chief complaint—particularly fatigue, pain, or sleep disturbance—and depressed mood may not be spontaneously reported 2
• Document symptom duration (minimum 2 weeks for major depression) and persistence (present most of the day, nearly every day) 1

Screening Instruments as Adjuncts

• Standardized questionnaires can identify potential cases but cannot make definitive diagnoses 1, 3
• Available questionnaires range from 1 to 30 questions with administration times under 1 to 5 minutes, yielding median likelihood ratios of 3.3 (positive) and 0.19 (negative) 1
• Critical caveat: Structured interviews have significant limitations, particularly with medical comorbidity, where false-positive rates can exceed 70% 3
• Use screening tools to prompt comprehensive evaluation in high-risk patients, not as diagnostic confirmation 4

Essential Differential Diagnosis

Medical and Substance-Related Causes

• Rule out delirium and medication-induced symptoms as primary considerations in medically ill patients 5
• Assess for systemic medical illnesses that commonly present with depressive symptoms, including endocrine disorders, neurological conditions, and chronic inflammatory states 5
• The overlap between neurovegetative symptoms of depression and physical illness symptoms creates diagnostic complexity requiring careful clinical judgment 5

Psychiatric Comorbidity

• Evaluate for anxiety disorders, adjustment disorders, and organic brain disorders, which are frequently misdiagnosed as depression by standardized instruments 3
• Assess suicide risk explicitly in all patients 2

Clinical Interview Structure

History Components

• Current episode characteristics: onset, triggers, symptom severity, functional impairment in work/social/personal domains 1
• Past psychiatric history: number of previous depressive episodes (critical for determining chronicity and recurrence risk) 2
• Family psychiatric history 1
• Substance use history 5
• Medical history and current medications that may cause or contribute to depressive symptoms 5

Reliability Considerations

• Mental health professionals using semistructured interviews achieve substantial to almost perfect agreement (kappa = 0.64-0.93) for major depression diagnosis 1
• Primary care physicians using semistructured interviews can achieve high agreement with mental health specialists (kappa = 0.71) 1
• Nonstandardized interviews yield lower reliability (kappa = 0.55-0.74), emphasizing the value of systematic symptom assessment 1

Key Pitfalls to Avoid

• Do not rely solely on standardized diagnostic interviews for definitive diagnosis, as they capture nonspecific syndromes and have poor specificity, particularly with somatic comorbidity 3
• Do not assume absence of depressed mood excludes depression—many patients present primarily with somatic complaints 2
• Do not overlook that depression is a systemic illness with pathophysiology overlapping other medical conditions, requiring consideration of bidirectional relationships 5
• Recognize that vague criterion definitions in structured interviews lead to diagnostic inaccuracy, necessitating clinical expertise for interpretation 3