The objectives of this study are to analyze the psychometric properties of the data collected with the European Portuguese version of the UCLA Loneliness Scale version 3 (UCLA-LS-3) and to evaluate levels of loneliness and perceived social isolation in Portuguese adults. 802 individuals aged 18 to 82 years (M= 35.12; SD= 15.67) responded to the scale, and reliability and validity analyses were conducted. The to...