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Clinical Global Impression Scale
Available in the public domain: Clinical Global Impression
Supplemental: Multiple Sclerosis (MS)
Exploratory: Amyotrophic Lateral Sclerosis (ALS) and Headache
Short Description of Instrument
The CGI is used to provide a global rating of illness severity, improvement, and response to treatment. It is a three-item observer rating scale and uses a seven-point rating scale. The CGI Scale is widely used in clinical psychopharmacology trials as an outcome measure.
Construct measured: Illness severity, improvement and response to treatment
Generic vs. disease specific: Generic
Means of administration: Self-administered
Intended respondent: Patient
# of items: 3
# of subscales and names of sub-scales: N/A
# of items per sub-scale: N/A
Comments/Special Instructions
The CGI Scale consists of three global subscales formatted for use with the Global Scoring Sheet. The Severity of Illness subscale assesses the clinician's impression of the patient's current illness state; it is often used both before and after treatment. The Global Improvement subscale assesses the patient's improvement or worsening from baseline, which is usually the beginning of a clinical trial. The Efficacy Index subscale attempts to relate therapeutic effects and side effects by deriving a composite score that reflects both the therapeutic effect and the concomitant adverse reactions or side effects.
The CGI is rated on a 7-point scale, with the severity of illness scale using a range of responses from 1 (normal) through to 7 (amongst the most severely ill patients).
Strengths/ Weaknesses: Relatively lengthy (~ 40 minutes for follow-up assessments). May be susceptible to baseline level of cognitive impairment, with a tendency for greater levels of change to be recorded for those moderately severely impaired, as compared with mild or severe impairments.
Psychometric Properties: May take over 40 minutes to complete baseline assessment and then ~ 40 mins per follow-up. Predictive validity, correlated against CDR, GDS, MMSE and FAST, was highly significant for most correlations.
Administration: Administration time varies with familiarity with patient. Clinician-rated.
Guy W. ECDEU Assessment Manual for Psychopharmacology. (Revised) Rockville, Md. : U.S. Dept. of Health, Education, and Welfare, Public Health Service, Alcohol, Drug Abuse, and Mental Health Administration, National Institute of Mental Health, Psychopharmacology Research Branch, Division of Extramural Research Programs. 1976.
Additional References:
Busner J, Targum SD. The Clinical Global Impressions Scale: Applying a Research Tool in Clinical Practice. Psychiatry (Edgmont). 2007;4(7):28-37.
Spearing MK, Post RM, Leverich GS, Brandt D, Nolen W. Modification of the Clinical Global Impressions (CGI) Scale for use in bipolar illness (BP): the CGI-BP. Psychiatry Res. 1997;73(3):159-171.


Document last updated June 2019