Clinical Global Impression Scales

The CGI is a standardized assessment tool used to measure treatment response among psychiatric patients, and is widely used in psychopharmacology trials as an outcome measure. It is designed to assess global severity of illness and change in the clinical condition over time. It consists of 3 global subscales: Severity of Illness; Global Improvement; Efficacy Index. Item 1 is rated on a seven-point scale (1=normal to 7=extremely ill); item 2 on a seven-point scale (1=very much improved to 7=very much worse); and item 3 on a four-point scale (from 'none' to 'outweighs therapeutic effect'). The CGI is typically administered several times during treatment to track progress. While it takes only about 5 minutes to complete, its use requires knowledge of the patient's clinical history in order for the clinician to determine change in condition.