Validity of the Problem Gambling Severity Index Interpretive Categories

The Problem Gambling Severity Index (PGSI) is a widely used nine item scale for measuring the severity of gambling problems
in the general population. Of the four gambler types defined by the PGSI, non-problem, low-risk, moderate-risk and problem
gamblers, only the latter category underwent any validity testing during the scale’s development, despite the fact that over
95% of gamblers fall into one of the remaining three categories. Using Canadian population data on over 25,000 gamblers, we
conducted a comprehensive validity and reliability analysis of the four PGSI gambler types. The temporal stability of PGSI
subtype over a 14-month interval was modest but adequate (intraclass correlation coefficient = 0.63). There was strong evidence
for the validity of the non-problem and problem gambler categories however the low-risk and moderate-risk categories showed
poor discriminant validity using the existing scoring rules. The validity of these categories was improved with a simple modification
to the scoring system.