Individual stress responses have been addressed by multiple theorists; yet there remains uncertainty concerning how contextual and individual factors interact during the process. In this thesis, I formulate and test a transtheoretical model integrating basic psychological needs (Deci & Ryan, 2002) theory and challenge and threat states (Blascovich, 2008) to better understand when and why environments might differentially affect appraisals. In contrast to previous work theorising a deterministic relationship between thwarting environments and threat appraisals, I hypothesized that in presence of needs thwarting, specified personality factors exacerbate or attenuate sensitivity to stress, and subsequent formation of challenge and threat-based appraisals.