Piece wise modeling was used so that reactivity and recovery could be modeled simultaneously within the same model, and reactivity and recovery were estimated separately by calculating separate time terms at Level 1 . Reactivity was calculated as the number of minutes before the sample’s peak level, and all subsequent values were coded as 0. Recovery was calculated as the numbers of minutes following peak level, and all prior values were coded 0. To examine associations between stress reactivity and recovery with substance use, we included the substance use dummycode, the reactivity time term, the recovery time term, and the cross-level Substance Use × Reactivity Time and Substance Use × Recovery Time interactions as predictors in the model.Although difficulties with stress regulation are related to more frequent substance use among users , less is known regarding whether psychobiological responses to stress relate to substance use and precede initiation of use in adolescence. Therefore, the present study investigated whether dampened HPA axis and emotion responses to stress were related to substance use in a sample of Mexican-origin adolescents who had experienced high levels of adversity. Findings suggested that differences in HPA axis and emotion responses to social-evaluative stress relate to—and in some cases temporally precede—substance use among these adolescents, although associations varied by poverty status and sex. Dampened corThisol reactivity to stress was related to use of alcohol by age 14 and vaping nicotine by age 16 among youth above the poverty line, although there was no evidence that corThisol reactivity to stress related to initiation of use of substances between ages 14 and 16. In turn, mobile rack dampened emotion responses to stress were related to substance use primarily in female adolescents.
Among female adolescents, blunted anger reactivity to stress was related to marijuana use by age 14, and blunted sadness reactivity and recovery to stress were related to use of alcohol by age 16 and use of marijuana by ages 14 and 16. Blunted happiness reactivity to stress was related to use of alcohol by age 16, regardless of sex, and to the emergence of use of marijuana and cigarettes between ages 14 and 16 among female adolescents who had not used these substancesby age 14. Differences in associations between stress reactivity and recovery to stress and substance use by poverty status and sex may be due to differences in adolescents’ access to substances or differences in motivation for substance use.Dampened corThisol reactivity to stress was related to use of alcohol by age 14 and vaping of nicotine by age 16 for youth above, but not below, the poverty line. These findings align with prior work suggesting that blunted corThisol responses to stress relate to riskier substance use four years later among adolescents . Differences in stress physiology have been related to greater substance use among users , as well as greater risk for substance use initiation among youth . Inability to elicit a corThisol response from a stressor may suggest inflexibility of the HPA axis, such that people are unable to mobilize biological resources in the context of stress. Dampened corThisol reactivity to stress may be indicative of difficulties with regulating stress, as strategies for emotion regulation have been linked with psychobiological responses to stress . For instance, prior studies have found that adolescents and adults with poorer emotion regulation show blunted corThisol reactivity to stress, often characterized by consistently high levels of corThisol . Furthermore, moderate corThisol responses to stress can promote executive function including emotion processing and behavioral inhibition during stress .
Stress responses may be particularly tied to emotion regulation during adolescence, when youth are particularly sensitive to social threat and are still developing strategies for emotion regulation . Although associations with alcohol use at age 14 were cross-sectional, most evidence regarding the effect of substance use on HPA axis function has been observed among heavy users , and we do not have heavy use in this sample given participants’ age. Therefore, a more likely pathway is that differences in the stress response confer risk for substance use. Interestingly, youth above the poverty line who used alcohol by age 14 had higher levels of baseline salivary corThisol compared to youth who had never used alcohol by age 14. Although adolescents had two hours in the laboratory environment to acclimate to space and to rule out an arrival effect , there is a chance that adolescents who showed higher levels of salivary corThisol at baseline may have been stressed in anticipation of the TSST, in line with previous findings that adolescents with anticipatory reactivity to stress may be at higher risk for substance use . An alternative possibility is that these youth tend to show chronically higher levels of corThisol output as well as dampened reactivity to the task, although this possibility seems somewhat unlikely given that there were no differences in corThisol across the recovery period. Associations between dampened corThisol responses and substance use only emerged for youth above the poverty line. This finding was particularly interesting given that this sample of adolescents was very low-income overall . We assessed differences by poverty status because youth living in poverty often experience additional stressors that can influence their risk for substance use. However, it is important to note that this sample is still low-income overall, such that results may not generalize to differences in socioeconomic status among wealthier adolescents. First, youth who experience relatively more adversity or more challenging home environments are more likely to show blunted corThisol responses to stress .
Therefore, blunted corThisol reactivity to stress may be more consistently related to substance use among youth above the poverty line, whereas blunted responses relate to environmental factors among youth below the poverty line. Second, associations emerged only for alcohol and vaping nicotine, which tend to be more commonly used among youth with higher family income . In this study, adolescents above the poverty line may have been more exposed to alcohol and vaping, specifically, compared to youth below the poverty line. Importantly, irrespective of family poverty status, adolescents may still be able to access substances that they find at home. Third, poverty status may influence adolescents’ motivations for substance use; stress may relate to substance use for youth above the poverty line, whereas youth below the poverty line may turn to less costly means of stress relief or may also use substances for alternative reasons. For instance, adolescents with lower parental education engage in fewer pleasurable substance-free activities, and may aim to use substances to amplify positive emotions . High basal corThisol or dampened corThisol reactivity to stress may be indicative of difficulties with emotion regulation , vertical shelving and difficulties with emotion regulation may more strongly relate to substance use for youth above the poverty line. Associations between stress responses and substance use may differ by levels of socioeconomic status, and it is important to note that the poverty rate was much higher in the present sample than in the county due to the inclusion criteria of the parent study. Therefore, findings may generalize to families who are lower on the distribution of income, but not to more affluent families. Future research is needed to examine whether adolescents’ access to and motivation for substances can explain why associations between dampened corThisol reactivity to stress and alcohol use by age 14 and vaping by age 16 differ by poverty status, and whether similar associations are observed among affluent youth.In addition to HPA axis responses to stress, we found that dampened emotion reactivity to stress was related to alcohol, marijuana, and cigarette use, particularly among female adolescents. Substance use may have been related to dampened rather than exaggerated emotion responses to the TSST because of the nature of this laboratory stressor. Although modified to be culturally sensitive and to avoid eliciting undue distress , the TSST can be a particularly taxing stressor. This may have caused youth to disengage rather than actively cope with the task and thereby manifested in dampened stress reactivity . Engagement in strategies such as distraction has been related to emotional and behavioral difficulties specifically for youth who show blunted corThisol responses to social stress . Additionally, these youth have backgrounds of high adversity and life stress which may have contributed to dampened emotion responses. Previous research has indicated that youth who experience adversity show reductions in activation of neural regions related to threat and emotion processing . Several associations between dampened emotion responses and substance use were unique to female adolescents, potentially related to sex differences in adolescents’ motivations for substance use .
It is important to note that although emotion responses to stress were more related to substance use in female than in male adolescents, male adolescents tend to be at higher risk for earlier substance use . Our results suggest that stress responses may be particularly related to substance use and substance use initiation among female adolescents, although male adolescents may have different motivations that place them at higher risk for substance use more generally. Prior research has found that female adolescents are more motivated to use substances to reduce stress and negative emotion, whereas male adolescents are more motivated to use substances for social benefits , and that stress is more strongly related to substance use in female than in male adolescents . Future research should investigate the factors that contribute to male adolescents’ risk for substance use. Alcohol and marijuana use may have been more consistently related to emotion responses than cigarettes or vaping because alcohol and marijuana are the most commonly used substances during adolescence and are often used to reduce stress . Cigarette use may have only related to happiness reactivity to stress but not sadness or anger reactivity because of the low prevalence of use in this sample, as cigarettes have declined in popularity over time especially among Latinx youth . Emotion reactivity to stress may not have been related to vaping of nicotine because vaping is more frequently used for experimentation and taste rather than to influence stress and emotion . Further information on adolescents’ motivation for use may provide insight regarding the mechanisms relating substance use and emotion responses to stress. Finally, sadness and happiness reactivity to stress were more consistently related to substance use than anger reactivity. Anger reactivity to stress was only related to marijuana use by age 14 among female adolescents, and this association was not maintained after transforming the data to account for skew. Studies that examine whether anger reactivity and recovery to stress relate to substance use can consider other paradigms or forms of stress that elicit a more robust change in anger. Substances are commonly used to reduce sadness and stress and to increase positive emotion , which may explain why associations emerged between sadness and happiness reactivity to stress, but not anger reactivity, and substance use. Although prior research has emphasized the role of negative emotions in motivation for substance use , dampened happiness reactivity to stress was uniquely related to initiation of cigarette and marijuana use between ages 14 and 16 among female adolescents. We also found that female adolescents who used marijuana and cigarettes by age 16 reported lower levels of happiness at baseline than female adolescents who never used these substances by age 16, but no differences in other emotions. It is possible that these youth use substances to promote positive emotion, or that lower positive emotion reactivity may indicate lower reactivity to other positive daily activities and greater inclination to use substances. Positive emotion has received relatively less attention in the context of stress responses, but the present findings suggest that future studies incorporating social-evaluative threat would be well-positioned to examine how happiness and different dimensions of positive emotion relate to substance use in the context of stress. Further research is needed to understand how dampened positive emotion reactivity to stress may confer risk for substance use in adolescence. Results at age 14 may suggest that substance use can influence adolescents’ stress reactivity to stress and ability to self-regulate within the context of stress. In turn, stress reactivity at age 14 may relate to substance use at age 16 through various mechanisms, such as through greater inclination to use substances to relieve stress, greater risk-taking, or greater susceptibility to peer pressure, which should be explored in future studies. There were limitations in corThisol assessment.