The Functioning Assessment Scale for Mental Health: Development and validation.

The Functioning Assessment Scale for Mental Health (FAS-MH) was successfully developed as a 37-item multidimensional scale grounded in the International Classification of Functioning, Disability, and Health (ICF).

• The final scale covers 34 second-level ICF categories across three domains: Body Functions, Activities and Participation, and Environmental Factors.
• Item generation was conducted in both Spanish and English.
• Content validation was performed through a two-round Delphi survey with expert panels of 20 and 12 professionals, respectively.
• The FAS-MH is described as the first instrument to comprehensively incorporate all ICF components for assessing functioning in individuals with mental disorders.

Confirmatory factor analysis supported a hierarchical model with four first-order factors and one second-order Functioning factor for the FAS-MH.

• The psychometric testing was conducted in a sample of 334 adults diagnosed with bipolar disorder, depression, or schizophrenia.
• The hierarchical model included four first-order factors nested under one overarching second-order Functioning factor.
• The dimensional structure was examined alongside internal consistency and relationships with other variables.

The FAS-MH demonstrated excellent internal consistency across its subscales and total scale.

• Cronbach's alpha ranged from α = 0.85 to 0.95 across the scale and its components.
• McDonald's omega ranged from ω = 0.90 to 0.96 across the scale and its components.
• These values indicate excellent reliability at both the subscale and total scale levels.

The FAS-MH showed moderate to strong correlations with established measures of disability, health status, and quality of life.

• Convergent validity was assessed through relationships with established measures of disability, health status, and quality of life.
• Correlations were characterized as moderate to strong, supporting the instrument's construct validity.
• Associations with clinical outcomes, symptom severity, or clinician-rated assessments were not explored in this study.

The study had several notable limitations including small content validation sample size and restriction to Spanish-language psychometric testing.

• Content validation was based on a small sample of experts (20 in round one, 12 in round two).
• Only the Spanish version of the FAS-MH was tested psychometrically.
• Associations with clinical outcomes, symptom severity, or clinician-rated assessments were not explored.
• The psychometric sample consisted exclusively of adults diagnosed with bipolar disorder, depression, or schizophrenia, which may limit generalizability.