How to Properly Assess the Global Assessment of Functioning (GAF) Score
The GAF should be rated by integrating information on both psychiatric symptom severity and level of impaired behavior/social functioning, with clinicians starting their assessment by evaluating conceptual disorganization and thought disorder, then progressing to assess conversation ability, activity level, and social/occupational functioning. 1
Core Assessment Framework
The GAF is a 0-100 scale that measures psychological, social, and occupational functioning comprehensively. 1, 2 Clinicians should rate by first evaluating the severity of psychiatric symptoms (particularly conceptual disorganization), followed by assessment of behavioral and social functioning impairments. 1 This hierarchical approach reflects how experienced clinicians naturally integrate clinical information.
Essential Information Collection
Before rating, gather comprehensive data across multiple domains:
- Psychiatric symptom severity using structured instruments like the Brief Psychiatric Rating Scale (BPRS), particularly focusing on conceptual disorganization, hallucinations, and thought disorder 1
- Social functioning including conversation ability, social withdrawal, and underactivity 1
- Occupational functioning and ability to perform work or school activities 1
- Activities of daily living and self-care capacity 1
- Physical health limitations that may impact functioning 3
Time Frame Specification
Always specify which time period you are rating: 2
- Current functioning (most common in clinical practice) 4
- Functioning at admission (for hospitalized patients) 4
- Highest level in past year (for longitudinal assessment) 4
- Lowest level in past week (for acute deterioration) 2
The choice of time frame significantly affects the score, and mixing time frames destroys reliability. 2
Rating Methodology
Starting Point Strategy
Begin rating from the middle of the scale (around 50) rather than top or bottom, as this reduces anchoring bias. 2 The middle-out approach allows for bidirectional adjustment based on clinical information.
Within-Interval Scoring
Each 10-point interval (e.g., 51-60) contains anchor points and examples. 2, 5 Use the specific anchor point descriptions and clinical examples provided in each interval to determine the exact score within that range. 2 Do not simply default to the midpoint of an interval.
Integration of Multiple Data Sources
Weight symptom severity more heavily than functional impairment when these conflict. 1 Research shows clinicians naturally prioritize conceptual disorganization and psychotic symptoms over social functioning deficits when assigning scores. 1
Critical Training Requirements
Brief training (even one hour) significantly improves GAF reliability from poor (ICC +0.48-0.59) to acceptable levels (ICC +0.60-0.83). 4 Without training, inter-rater reliability is unacceptably poor, even among experienced clinicians. 3, 4
Training should cover:
- The hierarchical decision-making process (symptoms first, then function) 1
- Specific anchor point definitions for each 10-point interval 2
- Time frame specification requirements 4, 2
- Practice with standardized vignettes or video cases 4
Common Pitfalls to Avoid
Do not conflate physical health limitations with psychiatric functioning - the GAF specifically measures psychological, social, and occupational functioning, not physical disability. 3 Clinicians often inappropriately lower GAF scores based on physical limitations.
Avoid systematic bias toward lower scores - clinicians consistently rate 2-3 points lower than trained research raters for the same patients. 3 Be aware of this tendency toward pessimism.
Do not use GAF as a disease severity measure alone - while GAF correlates with symptom severity, it is designed to measure functional impairment, not just symptom burden. 3 The scale integrates both dimensions.
Ensure adequate information collection - insufficient patient information is a major source of rating errors. 5 You cannot rate GAF accurately without detailed information about symptoms, social functioning, and occupational capacity.
Validity Considerations
The GAF shows strong correlation with disease severity measures (depression scales, symptom inventories) but this represents a limitation, not a strength - it suggests the scale may not adequately distinguish between symptom severity and functional impairment. 3 Be conscious of rating functional capacity independently from symptom burden when possible.
Inter-rater reliability between clinicians is poor (r=0.26) without standardized training, even in routine clinical settings. 3 This means GAF scores from different raters cannot be meaningfully compared unless both raters used identical training and methodology.
Documentation Requirements
When recording a GAF score, document: