How is gambling harm measured, and what is the Problem Gambling Severity Index?

Gambling harm is measured mostly through surveys that ask people questions, and the best-known tool is the Problem Gambling Severity Index, or PGSI: a 9-item screening tool used to measure at-risk behaviour in problem gambling.

Here is how the PGSI sorts people. Each of its 9 items is answered on a four-point scale from "never" to "almost always", and the item scores add up to a total between 0 and 27. A score of 0 describes someone who gambles but reports none of the 9 problems asked about. Those scoring between 1 and 2 are low-risk gamblers, with few or no identified negative consequences. Those scoring between 3 and 7 are moderate-risk, with some negative consequences. A score of 8 or more represents problem gambling, in which a person will have experienced adverse consequences from gambling and may have lost control of their behaviour.

Other tools exist, and the definition is not the same everywhere. Research by governments in Australia led to a definition without diagnostic criteria, built around difficulties in limiting money or time spent on gambling that lead to adverse consequences for the gambler, others or the community. In psychiatry, the DSM-5 re-classified the condition as an addictive disorder. An older screen, the South Oaks Gambling Screen, has declined in use because it overestimates false positives.

So what do the surveys find? Based on 2018 Health Survey for England data, the government review estimated that 0.5% of the population reached the threshold to be considered experiencing problem gambling, and 3.8% were gambling at elevated risk. In Europe, rates are typically 0.5 to 3 percent. These prevalence figures, meaning how common something is, differ because tools, definitions and years differ, so each figure belongs to its own survey, and the harm reaches beyond the gambler: around 7% of people in Great Britain were reported as affected by someone else's gambling.