Employment arrangements across industries and demographic groups have become increasingly precarious in recent decades. This shift has resulted in a growing proportion of the workforce that is exposed to risks and vulnerabilities associated with insecure and substandard employment. There is an urgent need to understand the role of employment precarity in increasing an individual's risk of adverse behavioral health outcomes, which are particularly prevalent among working-age adults and result in considerable loss of productivity in US workplaces. To address this critical issue, robust analyses of existing longitudinal data which allow for comprehensive measurement of individuals' experiences with employment precarity and their relationships with behavioral health are needed. Few existing studies, especially in the US, have sought to measure employment precarity comprehensively and longitudinally and, to date, no such studies have explored the relationships between the precarity of individuals' employment trajectories and their behavioral health. Existing studies of employment precarity have also failed to account for interruptions in employment and changes in jobs over time, despite the known impact of unemployment on adverse behavioral health outcomes. In light of these gaps in existing research, the proposed study will employ data from two National Longitudinal Survey of Youth (NLSY) cohorts (1979 & 1997) to define measures of employment precarity and employment variability and characterize their longitudinal trajectories (Aim 1) and model associations between employment precarity and substance use, two indicators of behavioral health (Aims 2 and 3). The extensive nature of the NLSY79 and 97 datasets will allow for characterization of disparities in employment precarity trajectories and cumulative employment variability, with the potential to elucidate key risk factors affecting the prevalence of precarious work. This pursuit, coupled with the proposed test of whether trajectories of employment precarity and variability are associated with adverse behavioral health in these two longitudinal datasets, addresses research gaps highlighted in the 2020 NORA Healthy Work Design and Well-Being report and can inform opportunities for intervention addressing intersections of work, psychological distress, and substance misuse across the life course. This study provides an excellent opportunity for mentored training and career development focused on the expansion and refinement of skills and knowledge necessary to purse the proposed research aims and career goals. My proposed career development plan will 1) build my understanding of behavioral health outcomes and mechanisms associated with employment, 2) expand my knowledge of advanced survey methodology, 3) develop my competency in statistical concepts for longitudinal analysis of survey data, and 4) strengthen my practical skills in statistical computing for the analysis of longitudinal survey data. Thes...