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 cortisol at baseline may have been stressed in anticipation of the TSST, in line with previous findings that adolescents with anticipatory reactivity may be at higher risk for substance use . An alternative possibility is that these youth tend to show chronically higher levels of cortisol output as well as dampened reactivity to the task, although this possibility seems somewhat unlikely given that there were no differences in cortisol across the recovery period. Associations between dampened cortisol 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 cortisol responses to stress . Therefore, blunted cortisol 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,cannabis grow equipment 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 cortisol or dampened cortisol reactivity may be indicative of difficulties with emotion regulation , 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 associations between income and substance use among more affluent families. Future research is needed to examine whether adolescents’ access to and motivation for substances can explain why associations between dampened cortisol 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 social-evaluative threat 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 cortisol 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 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 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 were more consistently related to substance use than anger reactivity. Anger reactivity 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 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, 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 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,cannabis grow racks 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 may confer risk for substance use in adolescence.Findings must be interpreted within the context of the study design. Results at age 14 may suggest that substance use can influence adolescents’ stress reactivity 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 cortisol assessment. The present study lacked data regarding current use of anxiolytics and antidepressants, both of which could influence cortisol responses. Estimates of cortisol recovery may be affected because participants were debriefed shortly after completing the TSST. Whereas other protocols collect all saliva samples prior to debriefing, the TSST was highly distressing for many participants in this sample, and debriefing occurred earlier to ensure adolescents were not distressed for longer than necessary . This decision may have resulted in higher levels of recovery than would have been experienced otherwise. Although we utilized a social stressor given the high salience of social threats during adolescence, future studies can assess whether similar results are assessed with respect to nonsocial stressors . Also, due to the low number of assessments, we needed to anchor responses at the sample peak rather than at each participant’s peak. We could not use analytic techniques such as Landmark registration because we would be unable to assess recovery for a subset of participants who peaked at the fourth time point. Future studies should include multiple assessments of salivary cortisol throughout the recovery period so that this technique can be used.
Because adolescents reported whether they had ever used each substance at age 14 and again at age 16, items may assess experimentation, and it is possible that adolescents may have only used a substance once and never again . Frequency of use over the past month or past year may be a better indicator of adolescents’ substance use and risk for problems with substance use in adulthood, although these outcomes had limited variability in the current sample at these ages. Future studies with greater variability in frequency or with slightly older samples should examine how frequency of use is related to differences in the stress response. Furthermore, without items regarding the context of daily use, it is difficult to determine the mechanisms by which differences in stress reactivity relates to substance use. Another important limitation of the present study is that stress responses were measured only at age 14, such that we cannot assess the stability of responses at age 14 and age 16 and cannot determine whether stress responses at age 14 confer risk for substance use at age 16 over and above current concurrent stress responses at age 16. Additionally, only three discrete emotions were measured, and participants were not able to report how they felt at that moment during the TSST. Potentially by using a different stress paradigm or passive assessment tools, participants could report their emotion as they experienced the stressor rather than immediately afterward in order to limit bias due to retrospective report and maintain consistency across ratings. We also had multiple ratings of emotion across the recovery period, but only one measure of emotion prior to the TSST. Future studies should employ experimental paradigms that allow for incorporation of more assessments of emotion during the stress task and therefore enable better estimation of emotion reactivity to stress. Results could also potentially vary by analytic approach, and other approaches such as longitudinal structural equation modeling can be used. Given the design of this study, multilevel models allow for all available data to be included, while allowing for timing of individual assessments to vary across participants and allowing for random intercepts and random slopes of reactivity and recovery. Finally, analyses were tested in a primarily Mexican-origin sample of adolescents with high levels of adversity and poverty, who may be at heightened long-term risk for substance use. We studied youth with high substance use risk because of our interest in how stress responses relate to substance use, as has been done in previous studies . We anticipated that the stress responses may be more related to substance use among youth who experience more major negative life events and chronic daily stressors, as these youth may be more inclined to use substances as a means of decreasing negative emotion as opposed to other purposes such as increasing positive emotion compared to other populations . Therefore, although our results suggest dampened stress responses may predict substance use in this sample, effects may be weaker in other adolescent samples with less adversity.