Psychological distress is determined and measured by the Kessler-10 (K10) scale.

Respondents are asked a series of questions about how often they felt particular feelings, including restlessness, worthlessness, hopelessness and nervousness, among others.

These responses are then scored and totalled up, providing an estimate of psychological distress. People are deemed to be distressed if their score is classed as "high" or "very high".