RESUMO
In recent literature, many researchers have highlighted that the feeling of loneliness can be considered a sign of relevant distress with short- and long-term consequences on the health of people who needs to be appropriately monitored and treated. In this view, the Interpersonal Acceptance-Rejection Loneliness Scale (IPARLS) has been developed to evaluate the subjective feelings and distress related to interpersonal loneliness and to overcome the limits of the previous scales; however, its psychometric characteristics have not yet been fully investigated. Starting from these considerations, two studies have been conducted. The first study, involving 688 adults (19-69 years; 51% females), assessed dimensionality, reliability, and validity of and tested the measurement invariance (MI) of the Italian version of the IPARLS. The second study, involving 205 adults (20-69 years; 51% females), investigated the relationship between loneliness and psychological adjustment. Results confirmed the unidimensionality of the scale and showed that it is reliable, valid, and fully invariant as a function of age and gender. Moreover, data showed a strong association between perceived loneliness and psychological adjustment. The IPARLS is confirmed to be a valid and reliable measure to investigate loneliness in the life cycle from clinical and research perspectives.