Development and validation of the Sources of Stress and Unease in Incarcerated Individuals Scale (SSUIS): a psychometric instrument for assessing inmate stressors in correctional settings. An exploratory study

Incarceration presents significant psychological and emotional challenges, increasing stress and vulnerability to mental health disorders. This study introduces and validates the Sources of Stress and Unease in Inmates Scale (SSUIS), a psychometric tool designed to assess stressors among male incarcerated individuals in Madrid, Spain. A four-phase design included interviews (n = 40), focus groups (n = 120), expert review (n = 11), and administration of a revised 52-item questionnaire to 365 second-degree male incarcerated individuals. Exploratory factor analysis identified five factors explaining 81.35% of the variance: (1) Dissatisfaction with food; (2) Occupational under-engagement; (3) Perceived negative treatment by correctional staff; (4) Poor sleep quality; (5) Perceived crime-based discrimination. All subscales demonstrated high internal consistency (α = 0.76–0.94 and McDonald’s Omega = 0.79–0.94) and strong convergent validity. SSUIS offers a reliable and valid measure of prison-related stressors, with potential applications in psychological assessment and intervention. Future research should examine its relevance across different institutions, individuals in different security levels, and inmates from other cultural or institutional contexts.