In the current society stress is highly increasing among young adult people. Indeed, they can be constantly subjected to social evaluative situations (job interviews/exams/performance evaluations) due to the increased competitiveness in the job market. Generally, individuals feel stress when external situations exceed their ability to cope with it. Anything that might be a challenge or a threat to well-being is a stressor. Some stressors are good for people’s life. Indeed, short term stress response permits the organism to mobilise energy to fight or flee from a threat enhancing its chances of survival (Cannon, 1932). On the other hand, some stressors are maladaptive and if prolonged over time they might have negative health consequences (McEwen & Gianaros, 2011). Face a stressful situation triggers the activation of a wide range of physiological responses such as the autonomic nervous system (ANS), the hypothalamus-pituitary-adrenal axis (HPA-axis), and the immune system, among others (Foley & Kirschbaum, 2010). The subjective appraisal of stress and the subsequent physiological responses differ from person to person according to some psychobiological factors. Among these differences, major stressful situation (i.e. to be unemployed) (Ockenfels, Porter, Smyth, J., Kirschbaum, Hellhammer, & Stone, 1995), some personality traits (i.e. optimism) (Creswell, Welch, Taylor, Sherman, Gruenewald, & Mann, 2005), or psychological state (i.e. appraisal of stress) (Tomaka, & Blascovich, 1994) play an important role in stress responses. Moreover, the dissimilar psychophysiological way to react to a stressful stimuli lead people to different outcomes (i.e. cognitive and behavioral performance) (Sandi & Pinelo-Nava, 2007). Therefore, in this thesis I am going to present the results of three studies focused on the antecedents and consequences of a psychophysiological responses to stress in a group of young adults individuals. The first chapter of this dissertation describes the evolutionary concept of the stress response and the main systems involved. Thus, I am going to present a short overview of the previous studies that focus on how these factors may influence the stress response. Finally, the chapter ends with the main objectives that will be developed in the empirical chapters. The second chapter presents the methodology used to perform the three empirical investigations. Particularly, it includes a description of the sample and the sampling process, the experimental design, the variables and measures used, as well as statistical analyses used to evaluate the hypothesis of the studies. Chapters third, fourth and fifth describe throughout three main empirical studies the influence of some antecedents and consequents factors involved in the psychophysiological stress response when individuals are subjected to an acute social evaluative challenge, such as a mock job interview. Particularly, chapter third describes the impact of to be a young adult unemployed looking for a job on the psychophysiological responses to stress. The study takes into consideration threat appraisal and cardiovascular responses to stress. The fourth chapter describes the role of a personality trait on the psychophysiological responses to stress and its impact on behavioral performance. It mainly discusses the role of threat appraisal on the relationship between optimism and displacement behaviors, as well as the impact of cardiovascular and cortisol responses to this relationship. The fifth chapter presents a study about the role of sex on the psychophysiological responses to stress and its effect on working memory. Mainly, it discusses the different impact of threat appraisal, cardiovascular responses and cortisol release between males and females’ young people and their effect on working memory. The sixth chapter includes a general discussion, strengths and limitations of these studies. Future directions for research on this topic are also included. The seventh chapter contains the main conclusions derived from the three studies included in this dissertation. Finally, the eighth chapter presents a general summary of the studies and main findings in Spanish.