Multistudy Validation of the Loneliness in Intimate Relationships Scale (LIRS) in a Polish Sample of Partnered Individuals

This study aimed to translate and validate the Polish version of the Loneliness in Intimate Relationships Scale (LIRS-PL). Following ITC guidelines, a multistep translation procedure was applied, and the psychometric properties of the LIRS-PL were examined across three studies involving 1,074 adults in romantic relationships. Confirmatory factor analysis supported a bifactor model as the best fit for the scale’s structure. The LIRS-PL showed high internal consistency for the total score ($\omega$ = 0.925 in Study 2; 0.923 in Study 3a; 0.941 in Study 3b) and satisfactory reliability across subscales: Detachment ($\alpha$ = 0.848–0.901), Hurt ($\alpha$ = 0.835–0.865), and Guilt ($\alpha$ = 0.669–0.798). Test–retest reliability over a period of 34–99 days was moderate (ICC = 0.68). Convergent validity was supported by correlations with measures of loneliness, interpersonal distress, and depressive and anxiety symptoms, while discriminant validity was indicated by weaker associations with social and family loneliness. These findings suggest that the LIRS-PL is a reliable and valid tool for assessing loneliness in romantic relationships in the Polish context, with potential applications in research and clinical practice.