Clinical Overview
The Clinical Global Impressions (CGI) scale is a widely-used, brief clinician-rated assessment instrument developed to provide a global evaluation of illness severity and treatment response across psychiatric conditions. Originally developed in the 1970s and refined for use in clinical trials, the CGI consists of three primary components: the CGI-Severity (CGI-S) which rates current illness severity, the CGI-Improvement (CGI-I) which assesses change from baseline, and the CGI-Efficacy Index (CGI-E) which evaluates the relationship between therapeutic effect and adverse events. The scale utilizes simple 7-point rating formats that capture clinician judgment based on their total clinical experience with the particular patient population. The CGI’s strength lies in its ability to provide a global clinical perspective that integrates multiple aspects of patient functioning and symptomatology into a single, easily interpretable rating. Its brevity and flexibility have made it an essential outcome measure in psychiatric clinical trials and routine clinical practice across diverse mental health conditions.
Key Validation Points
- Universal Clinical Validity – Extensively validated across virtually all psychiatric conditions with demonstrated sensitivity to treatment effects
- High Inter-Rater Reliability – Demonstrated good to excellent inter-rater reliability (ICC 0.70-0.90) when administered by trained clinicians
- Treatment Sensitivity – Proven responsiveness to pharmacological and psychotherapeutic interventions with established minimal clinically important differences
- Regulatory Recognition – Widely accepted by FDA and international regulatory agencies as a valid global outcome measure for psychiatric clinical trials
- Extensive Research Foundation – Used in thousands of clinical trials and research studies across all major psychiatric conditions with over 50 years of validation data
- Clinical Utility Evidence – Proven effectiveness in routine clinical practice with strong correlations to specific symptom rating scales and functional outcome measures
Primary Use Cases
- Clinical Trial Outcome Measurement – Primary or secondary endpoint in psychiatric clinical trials providing global assessment of treatment efficacy
- Treatment Response Monitoring – Longitudinal assessment of overall clinical improvement and treatment effectiveness across psychiatric conditions
- Clinical Decision Support – Global clinical rating to inform treatment modifications, medication adjustments, and care planning decisions
- Regulatory Approval Studies – Widely accepted by FDA and international regulatory agencies as a valid measure of clinical improvement
- Quality Assurance Programs – Standardized outcome measurement for healthcare quality improvement and program evaluation initiatives
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