Trends in associations between substance use and suicidality and patterns of current substance use in US adolescents: A repeated cross-sectional study

INTRODUCTION: Substance use and suicidal thoughts and behaviors (STB) among U.S. adolescents are both major public health concerns. Despite extensive research establishing a link between substance use and STB, little is known about how this relationship may be evolving over time. Understanding the changes in substance use and STB associations may illuminate factors driving the rise in adolescent STB and guide public health interventions. METHODS: The 1991-2021 national survey data from the Youth Risk Behavior Surveillance System were analyzed. Race/ethnicity-specific changes in the associations between each of the 12 substance use variables and 4 STB outcomes (suicidal ideation, suicide planning, suicide attempts, injurious suicide attempts) were assessed, by fitting logistic regression models with three-way interactions between time, substance use, and race/ethnicity, while adjusting for age and sex and accounting for the complex survey design. Current (2017-2021) adolescent substance use patterns were then identified using an unsupervised clustering approach, UMAP-HDBSCAN. RESULTS: Temporal trends varied by race/ethnicity for 36 of the 48 substance-STB combinations. Electronic vaping was unique in its non-decreasing association with all STB measures across all racial/ethnic groups (slopes [annual log-odds change] varied between 0.03-0.36). While cigarette use showed declining associations with STB among White adolescents, alcohol, heroin, injected, and methamphetamine use showed divergent trends across racial/ethnic groups. Clustering analysis identified five substance use behavioral phenotypes, including non-users (45.51%), poly/illicit users (20.84%), and other specific usage patterns (33.65%), with poly/illicit users reporting the highest rates of STB (31% suicidal ideation, 26% suicide planning, 16% suicide attempts, 6.3% injurious attempts). CONCLUSIONS: The finding that electronic vaping consistently showed an increasing association with all STB measures highlights the urgency of implementing suicidal prevention programs targeting adolescents who vape. Future research is needed to unveil the specific substance or combination of substances that contributed to the elevated risk of STB among poly/illicit users.