Major Depression Inventory (MDI)

Purpose and Clinical Application

The Major Depression Inventory (MDI) is a self-rating scale designed to measure the severity of depressive symptoms based on the ICD-10 and DSM-IV criteria for major depression. Developed by Per Bech and colleagues, it serves dual purposes as both a diagnostic tool and a severity measure.

Clinical Significance

The MDI is unique in its direct correspondence to diagnostic criteria for major depression, making it particularly valuable for both clinical assessment and research:

• Diagnostic screening: Based on official diagnostic criteria (ICD-10/DSM-IV)
• Severity assessment: Provides continuous severity scores
• Treatment monitoring: Tracks changes in depressive symptoms
• Research applications: Standardized depression measurement

Key Features

• 12 symptom items: Covering all major depression criteria
• 6-point Likert scale: 0-5 rating for symptom frequency/intensity
• Diagnostic algorithm: Can generate provisional DSM-IV diagnosis
• Severity scoring: Total score reflects depression severity
• Two-week timeframe: Assesses symptoms over past 2 weeks

Diagnostic Criteria Coverage

The MDI covers all nine DSM-IV criteria for major depression:

• Core symptoms:
  • Depressed mood
  • Loss of interest or pleasure (anhedonia)
• Additional symptoms:
  • Significant weight loss or gain
  • Insomnia or hypersomnia
  • Psychomotor agitation or retardation
  • Fatigue or loss of energy
  • Feelings of worthlessness or guilt
  • Diminished concentration or indecisiveness
  • Recurrent thoughts of death or suicide

Scoring and Interpretation

Severity Scoring:

• Total score range: 0-60
• 0-20: No or minimal depression
• 21-25: Mild depression
• 26-30: Moderate depression
• 31+: Severe depression

Diagnostic Algorithm:

• Major Depression: Requires ≥1 core symptom + ≥4 additional symptoms
• Symptom threshold: Items scored ≥4 (most of the time/all the time)
• Duration criterion: Symptoms present for at least 2 weeks

Psychometric Properties

• Internal consistency: Cronbach's α = 0.86-0.94
• Test-retest reliability: r = 0.82-0.92
• Sensitivity: 0.86-0.92 for major depression
• Specificity: 0.82-0.86 for major depression
• Concurrent validity: Strong correlations with HAM-D, BDI

Clinical Applications

• Primary care screening: Efficient depression detection
• Psychiatric assessment: Diagnostic aid and severity rating
• Treatment monitoring: Tracking therapeutic response
• Clinical trials: Standardized depression measurement
• Epidemiological studies: Population-based depression assessment

Advantages and Limitations

Advantages:

• Direct correspondence to diagnostic criteria
• Dual function as diagnostic and severity tool
• Strong psychometric properties
• Brief and easy to administer
• Available in multiple languages

Limitations:

• Self-report limitations may affect accuracy
• Cannot replace comprehensive clinical assessment
• May not capture all aspects of depression complexity
• Cultural factors may influence responses

Special Considerations

• Diagnostic use: Should supplement, not replace, clinical judgment
• Severity interpretation: Consider clinical context and functional impact
• Treatment monitoring: Regular administration can track progress
• Cultural sensitivity: Consider cultural expressions of depression