We aimed to investigate the extent to which Environmental Sensitivity (ES), as captured by the Highly Sensitive Person, 12-item scale (HSP-12), is distinguishable from traditional personality traits, contributes to psychological adjustment over and above personality, and if this contribution depends on the rearing environment. We also explored the HSP-12 psychometric properties and invariance across countries (UK and Italy) and samples (university and general population). Across multiple adult samples (N = 4459), we provided evidence that ES can be reliably assessed with the HSP-12 across countries and groups. We also showed that ES is distinguishable from established personality traits and is associated with lower well-being and negative affect, beyond personality. An environment perceived as caring played a buffering role.
