Brain Injury Is Prevalent and Precedes Tobacco Use among Youth and Young Adults Experiencing Homelessness

70%+ of youth and young adults experiencing homelessness (YYEH; 14-24 years old) smoke combustible tobacco. Little is known about the prevalence of acquired brain injury (ABI) among youth and young adult smokers experiencing homelessness (YYSEH) and its impact on tobacco use progression-the aim of our study. Through an interviewer-administered survey, YYSEH were asked about timing of tobacco use; exposure to causes of ABI; including brain oxygen deprivation (BOD; strangulation; accidental; choking games) and blunt force head trauma (BFHT; intentional; shaken violently; accidental); and perpetrators of intentional assault. Participants (n = 96) were on average 22 years old and from populations who experience structural disparities; including those minoritized by race (84.4%) and gender/sexual orientation (26.0%). In total, 87% of participants reported at least one exposure to BFHT and 65% to BOD. Intentional injury was more common than accidental. Furthermore, 60.4% of participants (n = 59) were classified as having ABI using the Brain Injury Severity Assessment. A significant proportion of YYSEH living with ABI were exposed to both BFHT and BOD prior to trying (68.5%, p = 0.002) and to first regular use (82.8%, p < 0.001) of tobacco. Among YYSEH with ABI; injury exposure occurred a median of 1 and 5 years before age of first regular tobacco use, dependent on injury mechanism. ABI from intentional violence is prevalent and precedes tobacco use among YYSEH.