The Nightmare Frequency Index-3: Reliability and Validity of a Brief Measure of Nightmares

The present research evaluated the psychometric properties of the Nightmare Frequency Index-3 (NFI-3), a brief self-report measure of nightmare frequency. Across 3 independent studies, the NFI-3 demonstrated a clear single-factor structure, acceptable internal consistency, and good temporal stability over an approximately 1-month interval. Evidence of construct validity followed the expected gradient, with strong associations with other multi-item nightmare measures, moderate associations with theoretically related constructs including trauma symptoms, negative affect, and psychological distress, and weak associations with hypothetically unrelated variables. Overall, the findings support the reliability and validity of the NFI-3 as a parsimonious instrument for assessing perceived nightmare frequency in research settings where brief measurement is desirable.