The Global Assessment of Functioning (GAF) is a numeric scale used by mental health clinicians and physicians to rate subjectively the social, occupational, and psychological functioning of an individual, i.e., how well one is meeting various problems in living. Scores range from 100 (extremely high functioning) to 1 (severely impaired).
The scale was included in the Diagnostic and Statistical Manual of Mental Disorders (DSM) version 4 (DSM-IV), but replaced in DSM-5 with the World Health Organization Disability Assessment Schedule (WHODAS), a survey or interview with detailed items. The WHODAS is considered more detailed and objective than a single global impression. The main advantage of the GAF is its brevity.[1]