Whereas cigarette use is more common among youth with lower socioeconomic status, marijuana, alcohol, and vaping are generally more prevalent among more affluent youth, potentially due to differences in cost, availability, and social norms . As a result, associations between stress reactivity and recovery and certain substances may differ by poverty status.The present study investigated whether adolescents’ HPA axis and emotion responses to the Trier Social Stress Test , a validated paradigm for eliciting social-evaluative threat, were related to the use of various substances among Mexican-origin youth growing up in a low-income, high-risk agricultural setting . Responses to a social stressor were selected because adolescents tend to be particularly responsive to social threats, compared to younger children and adults , and youth often use substances in peer contexts to reduce social stress or enhance social experiences. In line with prior research highlighting how people vary in the types of emotions they experience in response to stress , we examined changes in three emotions following stress: anger, sadness, and happiness. Therefore, rather than aggregating across emotions, we assessed unique effects of each emotion. We tested whether stress reactivity and recovery related to substance use among adolescents at heightened risk for substance use, in line with previous studies that have examined substance use initiation in high-risk samples . Most prior studies examining stress responses and substance use have been conducted in the context of adult substance users or with cross-sectional designs . Therefore, vertical racks we employed a longitudinal design to disentangle whether dampened psychobiological stress reactivity and recovery at age 14 precede the emergence of substance use initiation by age 16.

Models examined whether differences in adolescents’ HPA axis and emotion reactivity and recovery to the TSST at age 14 were related to a) use of substances by age 14, b) use of substances by age 16, and c) emergence of substance use between ages 14 and 16, excluding youth who had already used by age 14. Given the high levels of adversity in this sample, dampened psychobiological stress reactivity and recovery were predicted to be associated with use of alcohol and marijuana among these youth, in line with previous research . Although not previously tested with use of cigarettes and vaping, we examined whether dampened psychobiological reactivity and recovery would similarly relate to these substances which are also commonly used in adolescence. Finally, models examined whether associations between HPA axis and emotion stress reactivity and recovery and substance use differ by sex and poverty status. Given that female adolescents may be more inclined than male adolescents to use substances to reduce negative emotion , we predicted that associations between dampened stress reactivity and recovery and substance use would be stronger for female adolescents than male adolescents. Because poverty status can promote profiles of dampened reactivity and can influence the types of substances that youth use , we tested whether associations differ by poverty status.Participants were recruited as part of the CHAMACOS study, a longitudinal birth cohort study . The cohort is comprised of Mexican-origin adolescents and their primary caregivers living in the agricultural Salinas Valley in Monterey County, California. The study includes two cohorts: an initial cohort of participants followed from birth and a second cohort of 9-year-old children recruited partway through the study. At the time of CHAM1 enrollment in years 1999–2000, mothers of CHAM1 children were aged 18 or over and pregnant with the target child, under 20 weeks of gestation, eligible for California’s low-income health insurance program , receiving prenatal care, and planning to deliver at the county hospital.

These CHAM1 women were recruited at pregnancy clinics. Originally, 1,130 women were eligible, 601 were recruited, and 531 remained in the study after childbirth. Of their children, 325 CHAM1 remained enrolled in the study until age 14, with the majority of attrition occurring by age 3. Attrition was highest from pregnancy to delivery and was considerably lower since the assessment at age 5 . A second cohort of 300 nine-year-old children were recruited between 2009 and 2011, and they and their mothers have completed the same or comparable data collection activities as CHAM1 families since age 9 . Like the children from CHAM1, the mothers of CHAM2 children were 18 or older when pregnant with the child, primarily Spanish or English-speaking, eligible for Medi-Cal, and received prenatal care in the Salinas Valley. Retention rates for both cohorts were high between ages 9 and 14 . These adolescents were low-income and had high levels of social adversity. As described in detail in previous articles , roughly 40% of participants experienced an adverse life event between ages of 6 months and 5 years of age, over 60% of participants had a mother with depression at 1 or 3.5 years of age), over one in four adolescents had three or more adverse childhood experiences, and the sample generally reported high numbers of early life events .They then rested for 10 min. prior to the task and watched a 3 min. soothing video of the sea before being instructed to prepare a speech regarding how they are a good friend. They had 3 min. to prepare the speech and then presented the speech for 5 min. to two confederate ‘judges’ who appeared to be slightly older than the participant and who were described as experts in evaluating task performance. Immediately afterward, participants completed a mental arithmetic task involving serial subtraction for an additional 5 min. The confederates were trained to maintain neutral emotion and provide no positive feedback, and adolescents were also obtrusively video recorded throughout the speech and math tasks.

Participants were debriefed within 15 min. of completing the task to minimize distress. This protocol differed from the traditional protocol in the following ways for this population of Mexican-origin adolescents from high adversity backgrounds: confederates were from the local Salinas area and were from Latinx backgrounds; the difficulty of the math task was titrated such that participants would complete slightly easier math tasks if necessary to keep them consistently engaged with the task; participants were debriefed immediately after the TSST rather than after the full recovery period to avoid having participants feel sustained levels of distress; and gang-affiliated youth were excluded from the task due to both emotional outbursts and threats from at least one gang-affiliated youth and staff concerns about safety. An initial subsample of participants still showed a robust corThisol response, similar to that elicited by a traditional TSST, in spite of these modifications, before administering this protocol to the full sample .CorThisol—Adolescents provided four 1–2 mL saliva samples via passive drool throughout the task. They provided the first sample after spending over two hours in the laboratory environment, during which they completed benign surveys, and then resting in the lab for 10 min. The second sample was collected immediately after the TSST was completed, roughly 15 min. after TSST onset. The third sample was collected 30 min. after TSST onset, and the fourth and final sample was collected 60 min. after TSST onset. This sampling procedure was similar to previous administrations of the TSST . By collecting samples immediately after and 30 min. after TSST onset, we were able to collect saliva samples when corThisol levels were expected to increase post-TSST and increased our chances of capturing peak corThisol response in line with previous guidelines . Samples were frozen at −80°C and later thawed and assayed in duplicate using commercially available enzyme immuno assays in the SPIT lab, with low mean inter- and intra-assay coefficients of variation . Samples were assayed again if the optical-density intra-assay coefficient of variation was over 10%. Emotion—Adolescents also provided emotion ratings throughout the session. They rated the degree to which they felt happy, sad, and angry at four times: at baseline immediately prior to task onset, and at 15, 30, and 60 min. following task onset. Importantly, at 15 min.following task onset, weed drying rack participants completed two reports: they reported how they felt during the TSST, as well as how they felt at that moment. Participants completed two reports at this time point in order to assess emotion felt during the TSST without interrupting the task itself, and because emotion would be expected to change most between baseline and during the task, as opposed to immediately afterward when participants may feel relieved that the task is finished.

This resulted in a total of five emotion ratings, all of which were included in analyses. Adolescents reported each form of emotion on a scale from 1 to 10 . Brief and single-item measures of emotion have been commonly used in assessment of emotion responses to stress tasks and throughout the day . Substance Use—Adolescents also reported whether they had ever used alcohol, marijuana, and cigarettes in their lifetime at age 14 using items from the Monitoring the Future survey, with separate items for each substance . Two years later at age 16, adolescents again reported whether they had ever used alcohol, marijuana, or cigarettes or vaped nicotine in their lifetime.Models tested the association between adolescents’ stress reactivity and recovery at age 14 and substance use by age 14, substance use by age 16, and initiation of substance use between ages 14 and 16. Because participants provided multiple corThisol samples and emotion ratings throughout the protocol, we utilized a multilevel framework with observations nested within participants . Specifically, saliva samples and emotion ratings were variables at Level 1 and substance use was measured at Level 2. Multilevel models allow for missing data at Level 1, such that participants could be missing data on a sampling occurrence and still be included in analyses. Models included 905 total observations for corThisol, and 1,299 total observations for emotion. Number of corThisol samples and emotion ratings did not vary by gender, grade, poverty status reported substance use at age 14, and baseline levels of each emotion, all ps > .05. Multilevel models also allow for the number of observations and the specific timing of the collection of each saliva sample to vary across participants, so that the corThisol response to stress can be accurately modeled. This framework leveraged all data and enabled both stress reactivity and recovery to be modeled simultaneously. Participants reported substance use at ages 14 and 16, which enabled testing of whether stress reactivity and recovery at age 14 were related to substance use at age 14, substance use at age 16, and substance use initiation over two years among non-users. Substance use was collected at the level of the participant and was therefore included as a predictor of stress reactivity and recovery , and models tested whether differences in the magnitude of stress reactivity and recovery at age 14 related to whether adolescents had ever used each substance by ages 14 and 16. It is important to note that we consistently model corThisol and emotion at age 14 as the outcome, even though differences in the stress response are thought to be a risk factor for substance use at age 16. This approach is necessary statistically, as other approaches are unable to simultaneously model stress reactivity and recovery with this number of time points. This modeling also allows for piece wise modeling. There are a total of four samples for corThisol and five reports of emotion, both of which allow for piece wise assessment. Although three time points are generally needed to predict a linear trend, this modeling of all time points allows for HPA axis recovery to be computed using only two time points and for emotion reactivity to be computed using two time points. Alternative approaches include creating another index to test as a predictor of substance use, but these indices generally involve exaggerated error terms or violate staThistical assumptions by assuming no error for each value . Conceptually this model is appropriate because, just as a correlation reflects a bidirectional association, this model tests the association between substance use and differences in stress reactivity and recovery, irrespective of which is the predictor versus outcome. A similar approach has been used in previous papers . Adolescents’ substance use was dummy-coded . Separate models predicted corThisol, anger, sadness, and happiness as a function of adolescents’ substance use. Prior research has highlighted that multilevel models are generally robust to violations of assumptions, including having skewed outcome variables .