Adolescents and young adults represent 25% of the sexually-active population in the U.S., yet account for about half of all sexually transmitted infections annually. Latino youth have over 4 times the rate of HIV infection and 3 times the rate of AIDS compared to non-Latino white youth. About 20% of young Latinos report using drugs or alcohol prior to sexual intercourse. While these issues raise important public health concerns, the emergence of substance use and sexual risk-taking behaviors among Latino adolescents remains understudied. Sex and stress hormones operate together (e.g., Zakreski et al., in press) and recent research has begun investigating how these hormones couple to predict externalizing behavior (e.g., Johnson et al., 2014). However, it remains under-studied how these hormones operate together in relation to risky behavior in Mexican American adolescents.
The present study uses a longitudinal birth cohort study of Mexican American families in California called the Center for the Health Assessment of Mothers and Children of Salinas. Hormone reactivity (cortisol, testosterone, and DHEA) was measured in response to a modified TSST at age 14. Youth reported on a number of risky behaviors including age of sex (e.g., oral sex, vaginal intercourse) and substance use initiation at age 16.
Linear regression was used to examine the link between hormone reactivity to the TSST and risky sexual and substance use behavior. Results revealed significant interactions for participant sex by testosterone reactivity (t=-2.53, p<0.05) and cortisol by testosterone reactivity (t=-2.51, p<0.05) in prediction of sex initiation. Among girls, high testosterone reactivity was linked with earlier age of sex initiation regardless of cortisol reactivity, but among boys, the combination of high cortisol and high testosterone reactivity was linked with earliest age of sex initiation. Higher cortisol reactivity to the TSST was associated with earlier age of alcohol use for both boys and girls (t = -2.58, p < 0.05).
Examining biological factors related to risk-taking may help explain adolescent problem behaviors that predict adult disease, which can inform prevention. Results indicate stress-related testosterone changes are positively associated with earlier initiation of sex behavior in girls, whereas for boys, the combination of high testosterone and cortisol reactivity predicted early age of sexual initiation. This is commensurate with prior research suggesting that testosterone in females is more robustly related to behavioral outcomes (e.g., Halpern, 1997). Both boys and girls with higher cortisol reactivity may be turning to substances such as alcohol earlier to dampen their heightened arousal.