Background. The literature documents that functional impairment is associated with affective
disorders. Nevertheless, the choice among thorough, yet brief, well-validated assessments of
functional impairment is limited. The objective of this study was to evaluate the psychometric
properties of a brief scale of functional impairment, the Range of Impaired Functioning Tool
Method. The study sample included subjects who presented with major depressive disorder at
intake into the NIMH Collaborative Depression Study (CDS). The LIFE–RIFT is composed of
items that are included in the Longitudinal Interval Follow-up Evaluation (LIFE). The reliability
and validity were examined using data from LIFE–RIFT assessments conducted at four points in
time: 6, 12, 18 and 24 months after intake into the CDS.
Results. Cross-sectional one factor models accounted for the covariance structure among the four
scale items. A longitudinal factor model, with an invariant factor structure over time, also fitted the
data well and indicated that the scale items are measures of one construct, namely functional
impairment. The internal consistency reliability of the scale was supported with alpha coefficients
ranging from 0·81 to 0·83. The inter-rater reliability intraclass correlation coefficient (ICC) was 0·94.
Mixed-effect linear regression models showed that those in episode were significantly more impaired
than those in recovery. Furthermore, in analyses of predictive validity, impairment was positively
associated with subsequent recurrence and negatively associated with subsequent recovery.
Conclusions. This psychometric evaluation provides empirical support for the reliability and
validity of the LIFE–RIFT, a brief measure of functional impairment.