I googled Assessing Functional Impairment (hoping to find measures for functional impairment due to psych problems [to use for initial evaluation and then on follow-up to see if treatment has made any meaningul difference]) and found the following book: (I’m sure there are free tools on the net for this).
Barkley Functional Impairment Scale (BFIS for Adults)
Russell A. Barkley
Size: 8″ x 10½”
Convenient Wire Binding
A Paperback Original
Price: $155.00 $131.75
To diagnose a mental disorder or evaluate a disability claim, clinicians must assess functional impairment—not just the presence of symptoms. Meeting a key need, the Barkley Functional Impairment Scale (BFIS for Adults) is the first empirically based, norm-referenced tool designed to evaluate possible impairment in 15 major domains of psychosocial functioning in adults. Featuring both self-report and other-report forms (for example, spouse, parent, or sibling), the BFIS is reliable, valid, and user friendly. The long version takes the average adult 5-7 minutes to complete, and the Quick Screen takes only 3-5 minutes. Complete instructions for scoring and interpreting the scale are provided.
What does it do?: Assesses psychosocial impairments in 15 domains of major life activities.
Age Range: 18-89
Administration Time: Long Form: 5-7 minutes. Quick Screen: 3-5 minutes.
Format: Self-report plus other-report (for example, spouse, parent, or sibling) rating scales.
Cost of Additional Forms: No cost—purchasers get permission to reproduce the forms and score sheets for repeated use.
See also the Barkley Adult ADHD Rating Scale—IV (BAARS-IV), which measures current and recollected ADHD symptoms, and the Barkley Deficits in Executive Functioning Scale (BDEFS for Adults), which assesses clinically significant executive functioning difficulties.