Background: Previous studies suggested that item responses on the 6-item Kessler Psychological Distress Scale (K6) exhibit characteristic distributions among the general population. To confirm the reproducibility of these findings, we conducted a pattern analysis of the K6 item responses using large-scale data from a US representative survey.
Methods: Data were drawn from the 2016, and 2017 National Health Interview Survey in the United States (33,028, and 26,742 individuals, respectively). We analyzed the patterns of item responses for the six items using normal and logarithmic scales and proposed a model of item responses.
Results: The lines for item responses showed the same pattern among the six items, characterized by crossing at a single point between "none" and "a little," and parallel patterns from "a little" to "all of the time" on a logarithmic scale. The ratio of "some" to "a little," "most" to "some," and "most" to "all of the time" were similar across the six items. The model of item responses, which was based on the findings that the decreasing ratios of "some" to "a little," "most" to "some," and "all of the time" to "most" were similar across the six items, explained the characteristic patterns of item responses.
Conclusion: These results provide further evidence that item responses on the K6 follow a particular distribution pattern among the general population.
Keywords: Clinical psychology; Epidemiology; Psychiatry; Public health.