为一篇英语学术论文提供一份简短的摘要，并指出论文的主要贡献是什么。
英语学术论文全文或者摘要。
Abstract:

This paper examines the effects of social media usage on psychological well-being in young adults. A survey was conducted on 300 university students between the ages of 18 and 25. Results showed a significant negative correlation between social media usage and well-being, with higher usage leading to lower levels of well-being. Furthermore, the study found that social comparison and fear of missing out were mediators in this relationship. The main contribution of this paper is the identification of the specific psychological mechanisms through which social media usage affects well-being in young adults.

主要贡献：鉴定社交媒体使用对年轻成年人心理幸福感的影响，并明确了社交比较和错过恐惧是其中的中介变量。