Assessing harm severity: a Rasch analysis of the gambling harm measure

The Gambling Harm Measure (GHM) is a 16-item self-report instrument used to measures gambling-related harm (GRH) across its six principal domains. Unlike other GRH measures, the GHM uses multiple items to assess harm along a gradient of within each of its principle domain (excluding illegal acts). The objective of this study was to evaluate this severity gradient using Rasch analysis. Data from 2,941 respondents were obtained from three independent surveys, two conducted in the American state of Massachusetts and one conducted nationally across Canada. Item thresholds varied within each domain, providing evidence that the GHM can capture harm across a gradient of severity. There was evidence of differential item functioning (DIF), with younger adults and those participating in more harmful gambling formats (e.g. electronic gambling machines, casino table games) being more likely to endorse several items on the GHM. Finally, we identified three discrete categories of GHM scores: mild harm included individuals endorsing 1–6 items; high harm included individuals endorsing 7–13 items; and severe harm included individuals endorsing 14 or more items. This study provides support for the GHM as a valid measure of GRH that can capture both the range and severity of harm experienced by individuals who gamble.