Language Identity and Mental Health Disparities among Multilingual 1.5 Generation Asian/Asian American Immigrant Young Adults: A Mixed Methods Study - Data show that Asian/Asian American immigrants have experienced a relatively high level of mental health and other health conditions during and after public health crises. There are multiple reasons, including a language barrier, along with its impacts on isolation and marginalization, and a rise in crime and related incidents directed to Asian groups. We will focus on the components of the language barrier (language proficiency and language identity) and its effect on mental health. 1.5 generation Asian/Asian American immigrant young adults—those who migrated to the United States with their parents (1st generation) from Asian countries when they were children aged between 5 and 17, have been living in the United States at least 12 months, and current ages are between 18 and 29—are particularly vulnerable to adverse health consequences. Most of them begin using English as an additional language (L2) once they arrive in the United States, after mainly using a first language (L1) from their parents’ country of origin. However, little research to date has examined how learning an L2 among 1.5 generation Asian/Asian American immigrant young adults informs their sense of acceptance, inclusion, and identity as well as their acculturation, socialization, and psychological well-being in American society. To close this research gap, the objective of the proposed work is to investigate the association between learning an L2 and adverse mental health consequences among 1.5 generation young adults from Asian/Asian Americans. The central hypothesis of this study is that for 1.5 generation Asian/Asian American immigrant young adults, those who grew up affiliating with one culture and now may also need to affiliate with a new dominant American culture, are more likely to experience psychosocial adversity and mental health conditions. This project has two specific aims, using a mixed-methods research design. First, using quantitative analysis, we will determine the extent to which perceived language proficiency/language identity in 1.5 generation Asian/Asian American young adults is associated with psychological well-being and mental health (Aim 1). Aim 1 will be accomplished through a cross-sectional quantitative, online study sent to approximately 600 potential participants in the San Francisco Bay Area, California, with the desired sample size of 146 (F-squared effect size = 0.15, α = 0.05, Power = 0.8). Second, using qualitative analysis, we will gain an in-depth understanding of experiences with acculturation and how these experiences relate to their perceptions of language skills and psychological well-being/mental health consequences (Aim 2). We will conduct 5 focus group discussions and 20 subsequent in-depth interviews who participated in the quantitative survey from Aim 1 to further investigate varied factors affecting health before, during, and after immigration. In addition, we will assess the complexity of language: the potential positive effect of higher perceived home language (L1) or additional language (L2) proficiency on successful adjustment in American society.