Measurement Invariance of the Five-Factor Narcissism Inventory-Short Form According to Psychological Treatment History.

The Five-Factor Narcissism Inventory-Short Form (FFNI-SF) is the only extant scale that efficiently measures narcissism at the three-factor level (antagonism, agentic extraversion, and narcissistic neuroticism). Individuals with significant narcissistic dysfunction are frequently seen in clinical settings. However, there has been limited testing of measurement invariance (MI) in narcissism measures, especially multifaceted ones, across clinical and nonclinical groups. This study examined whether the FFNI-SF operates equivalently across individuals with and without a psychological treatment history. Using exploratory structural equation modeling (ESEM), we tested MI at four levels-configural, metric, scalar, and residual-in 473 community participants, 36% of whom had a psychological treatment history, current and/or lifetime. Results indicated scalar and residual invariance, suggesting that the FFNI-SF is valid for comparing narcissism traits at both the latent and observed score levels between treatment history groups. Latent mean comparisons revealed that individuals with a treatment history scored significantly lower on antagonism and higher on neuroticism compared to those without a treatment history. These findings highlight that narcissism's underlying dimensions may manifest differently in clinical samples and support the FFNI-SF as a viable multidimensional measure for capturing nuanced expressions of narcissistic traits across clinical and nonclinical contexts.