UC Davis

Suicide is the second leading cause of death for youth in the United States and the rates are continuing to rise. Unfortunately, national policy efforts to combat this increase in youth deaths by suicide have made little difference. Suicidal thoughts and behaviors (STB) disproportionately affect female adolescents, and youth of color, including Latino youth. To date, there have been few longitudinal studies of adolescent STB in Latino adolescents, thus, many of the prospective risk factors for suicidality in these populations are not well understood. Additionally, there is limited research which has examined the neurobiological predictors of STB in community or clinical adolescent samples across all genders and ethnicities. Given this imminent and intensifying public health crisis, additional investigations are needed to examine and understand both proximal and distal factors related to the increase in adolescent STB. Moreover, as the US becomes more ethnically diverse, risk and protective factors which influence both the general population as well as specific ethnic minorities should be examined, including environmental, social, and biological factors which may act to either ameliorate or exacerbate rates of youth STB. This dissertation investigated: (1) the associations between psychosocial and culturally specific factors and the growth of STB from early to late adolescence; (2) the role of the autonomic nervous system (ANS) in stress activation during social exclusion and its relation to concurrent and prospective STB in late adolescence; and (3) whether pubertal timing moderates the link between parasympathetic stress activity and concurrent and subsequent STB in clinically high-risk adolescent females. In Paper 1, female sex and later generation status were associated with increasing prevalence in STB across adolescence, and family conflict and peer conflict predicted increased STB whereas greater familism predicted less STB, in Mexican-origin youth. In Paper 2, prior STB was associated with lower sympathetic activity at baseline and during social exclusion, and prospective STB was predicted by lower basal ANS activity paired with greater ANS activation during social exclusion, in Mexican-origin youth. In paper 3, lower baseline parasympathetic activity and earlier pubertal timing were associated with prior STB, whereas girls with later pubertal timing and higher parasympathetic activity during a speech task were buffered from endorsing STB one year later. In summary, this body of research suggests that interpersonal processes, especially within the family, are critical for understanding suicidality risk in Mexican-origin adolescents. Additionally, basal autonomic activity may be a biomarker or a physiological “scar” of prior suicidality whereas certain patterns of autonomic stress activation may confer greater risk for prospective STB years in advance. Lastly, the female pubertal transition confers risk for STB and later pubertal timing may provide a protective buffer against STB for those youth who display dysregulated physiological responses to stress.