The 20-item Gambling Harms Scale (GHS-20): Benchmarked to health utility using propensity weighting and control for comorbidities

Measuring gambling-related harm is crucial for public health initiatives, but existing screens like the Problem Gambling Severity Index have limitations. The 10-item Short Gambling Harms Screen addresses some gaps, but lacks comprehensive domain coverage and robust validation against health utility benchmarks. This study aimed to develop and validate an extended 20-item Gambling Harms Scale. Objectives included achieving better representation across harm domains, selecting items based on unique associations with health utility decrements, and benchmarking the scale's scores against health utility. Data were collected from 2,603 Australian adults who gambled in the past year. Participants completed 31 candidate harm items, measures of gambling problems, quality of life, and health functioning. Item selection utilised latent trait modelling and lasso regression. The final scale was benchmarked against health outcomes using propensity score weighting to balance demographic factors and generalised additive modelling to control for comorbidities. Lasso regression identified items providing unique explanatory information, resulting in the 20-item harm scale, which includes items from all six gambling harm domains. The extended scale demonstrated excellent reliability (alpha=.98, omega=.90), correlated positively with the PGSI (r=.78) and negatively with health utility (r=-.38), but statistically was not a meaningful improvement on the 10-item scale. GAM analysis revealed a significant, near-linear negative relationship between harm scores and health utility, with statistically significant decrements observed even at low scores. Like the shorter scale, the extended scale is psychometrically robust, and can comprehensively assess gambling harm and calculate population harm burden.