Purpose: This study aimed to analyze the influence of narcissism on self-esteem and social media addiction. In addition, it highlights the consequences of social media addiction through internal factors such as self-esteem and external factors such as life satisfaction. It also examined the regulatory role of personality traits in this context. Participants and Methods: Conducted in Ho Chi Minh City, it surveyed 426 Generation Z individuals aged 13– 26 spending over two hours daily on social media, using convenience sampling. Data analysis and reliability assessment were done with SPSS 29, and SmartPLS 4 evaluated the linear structural model. Results: The study has demonstrated that narcissism among Generation Z significantly influences life satisfaction. The results indicate that narcissism plays a crucial role in determining the self-esteem of Generation Z. Furthermore, individuals exhibit varying levels of narcissism, which are positively related to various online social activities. Therefore, high levels of narcissism are likely to lead to social media addiction. Those who exhibit symptoms of social media addiction tend to have lower self-esteem because they perceive social media as a safe space where they can express themselves. However, each individual possesses unique personality traits, and this study has proven that specific personality traits such as Agreeableness and Openness impact the life satisfaction of Generation Z. Conclusion: The study investigated how narcissism, self-esteem, and social media addiction affect life satisfaction among Generation Z, exploring their complex interplay and mental health implications. It emphasized Gen Z’s widespread social media engagement and addiction risks, impacting mental health and emotional satisfaction. Additionally, it highlighted the influence of personality traits on life satisfaction. The examination scrutinized the intricate relationship between self-esteem and narcissism, stressing its nuances, especially among Generation Z.

Brand loyalty has a crucial role in the business and wins the mind of the customers is the key mission of any brand. On the other hand, consumers use brands to express themselves, position and integrate the brand image into their own identity. Hence, this study aims to find out the relationship between brand credibility, self-brand connection, and brand identity to brand loyalty in the context of Apple's brand. The study is quantitative research, data is surveyed in a single time collected from a population. 420 questionnaires are distributed to young people who are studying and working in Ho Chi Minh City and they are the current Apple customers. The finding of the research was shown that there has a mediating role of self-brand connection and brand identity in the relationship between brand credibility and brand loyalty. Also, brand identity has a positive impact on a self-brand connection. The findings also implied to the managers must be aware to build up the brand of products, it could increase the brand loyalty of customers. The results were also contributed to the knowledge of self-congruity theory about the self-brand connection would affect the relationship. Keywords: Brand credibility, self-brand connection, brand identity, brand loyalty.

Against the backdrop of Vietnam's booming e-commerce market, this study explores how social media influencers shape young people's online purchasing intentions. The research addresses a significant research gap regarding the inconsistency in the distribution of influencer attributes and the scarcity of empirical evidence on the parallel mediating roles of attitude and perceived credibility in the Vietnamese market. The study integrates Theory of Planned Behavior (TPB) and Source Credibility Theory. Specifically, three influencer attributes-expertise, credibility, and attractiveness-are considered inputs influencing purchasing decisions through two psychological mediating mechanisms: attitude and perceived credibility. The study employs a quantitative approach, collecting data from 442 eligible respondents aged 16-30 in Vietnam over a six-month period. Data were analyzed using partial least squares (PLS-SEM). All eight hypotheses were accepted, demonstrating a dual mediating mechanism in which expertise and credibility of influence disrupt purchase intention through two mediating variables: attitude and perceived trust level. Attitude, in particular, was the strongest predictor, proving that intrinsic psychological value is more important than the external attributes of the influencer. This result confirms a strong behavioral shift towards content over form among Vietnamese youth, where physical attractiveness has the weakest influence. Because attitude is the primary determinant, businesses need to prioritize content strategy over personal image, as this factor is identified as a crucial element in shaping Gen Z's purchase intention. Market budgets should shift towards consulting experts such as KOCs or evaluators with genuine expertise. This study has several novel aspects compared to previous studies. Previously, research on the theory of planned action and source trust within a single model has been shown to influence influencer activity in purchase intention. Simultaneously, the TPB (Theory of Planned Behavior) has been expanded to focus on mode as a central evaluation mechanism. The study also clarifies the mediating role of influencer attributes indirectly impacting purchase intention through attitude and credibility. The study provides evidence in Vietnam showing that Gen Z prioritizes expertise and trustworthiness over the attractiveness of the influencer.