A new look at the construct validity of the K6 using Rasch analysis

Area of Science:

• Psychometrics
• Mental Health Assessment
• Statistical Psychology

Background:

• The Kessler six-item psychological distress (K6) scale is a common tool for screening mental disorders.
• Limited data exists on the K6 scale's rating scale performance and dimensionality structure.

Purpose of the Study:

• To evaluate the construct validity and rating scale performance of the K6 scale.
• To assess the dimensionality structure of the K6 scale in a population-based sample.

Main Methods:

• Rasch partial credit analysis was employed.
• A population-based sample of 7596 participants was utilized.
• Item fit statistics and response patterns were analyzed.

Main Results:

• The K6 scale's five-point rating scales demonstrated appropriate use for differentiating psychological distress.
• Evidence for unidimensionality was found, with potential for a second dimension in specific items.
• Most items fit the Rasch model, indicating valid response patterns for the general population.

Conclusions:

• The K6 scale exhibits construct validity and is a useful instrument for assessing psychological distress in the mid-aged general population.
• Rasch analysis supports the K6 scale's utility and validity.
• Further research is recommended to explore the scale's unidimensionality.