The Effect of Early Life Stress on Subjective Fear and Electrodermal Response Reactivity in an Adolescent Community Sample

Past research demonstrates that a stressful environment early in life can have profound implications on an individual’s ability to regulate their emotions. One method that researchers use to assess abnormalities in emotion regulation is fear conditioning, where differences in the speed or strength with which one learns about unpleasant stimuli can indicate dysregulation. Currently, the literature is in conflict about whether those who have experienced early life stress (ELS) will show exaggerated or blunted responses to stressful stimuli, but both can cause problems later in life. The present study used a fear conditioning paradigm to further clarify the relationship between ELS and physiological reactivity during a fear conditioning task using a community sample of adolescents. We predicted that adolescents with greater reported levels of ELS would show exaggerated responses to the CS+ during acquisition and extinction. Additionally, we predicted that adolescents with greater levels of ELS would show lower rates of discrimination learning. Thirty-seven participants completed the Risky Families Questionnaire (RFQ) and the teen form of the Alabama Parenting Questionnaire (APQ) to measure cumulative ELS and had their skin conductance response measured during a fear conditioning task to assess their physiological reactivity. Regression analyses revealed that, contrary to our hypothesis, adolescents who reported higher levels of ELS subjectively reported less fear, but showed stronger physiological responses during the acquisition and extinction phases of the fear conditioning task which was in accordance with our hypothesis. Contrary to our hypothesis, analyses showed that individuals with higher indices of ELS showed greater discrimination learning during acquisition. Overall, this study highlights the importance of trans-diagnostic approaches to inform early and effective interventions. ELS AND PHYSIOLOGICAL STRESS REACTIVITY 4 The Effect of Early Life Stress on Subjective Fear and Electrodermal Response Reactivity in an Adolescent Community Sample. A stressful environment early in life has been associated with numerous negative physiological and psychological outcomes (Repetti, Taylor, & Seeman, 2002). A stressful early home environment, which is often marked by exposure to events like parental death, unemployment, and physical, verbal or sexual abuse, has been associated with increased risk for psychiatric disorders, including anxiety (Sharma, Prakash, and Kalra, 2016), depression, suicide, PTSD, conduct disorders and drug abuse (Lai & Huang, 2011). At the same time, early life stress (ELS) has been associated with a number of physical health risks later in life, including increased risk for chronic, noncommunicable diseases like ischemic heart disease, cancer, chronic lung disease, skeletal fractures, liver disease, type II diabetes (Lai & Huang, 2011), and poor immune function (Taylor, Lerner, Sage, Lehman, & Seeman, 2004). Given this prolonged suffering, the risk for mortality, and the healthcare costs that are caused by these physical and mental illnesses, it is imperative that researchers uncover mechanisms by which early life stressors create risk for poor health outcomes early in life. This research can help inform prevention and intervention efforts earlier in development, when they may have a stronger impact on stress-exposed individuals. Defining Early Life Stress Researchers have defined ELS in a number of ways: singular traumatic events (e.g. car crash or natural disaster; Lai & Huang, 2011), exposure to repeated abuse or neglect, or checklists of major life stressors such as frequent moves, divorce, and unemployment (Petchel & Pizzagalli, 2011). Unfortunately, many of these methods ignore the co-occurrence of multiple ELS AND PHYSIOLOGICAL STRESS REACTIVITY 5 stressors in the early environment. In fact, many studies show that early life stressors are more likely to be cumulative rather than specific isolated events. One study that analyzed adverse early experiences in childhood found that two-thirds of their sample population that reported at least one adverse childhood experience (ACE), also reported another ACE. They also found that the presence of one ACE significantly predicted the occurrence of multiple (Dong et al., 2004). One explanation for the occurrence of cumulative adversity is the fact that these stressors are often rooted in the socioeconomic context of the family. A study by Gary Evans and Kimberly English (2003) established that a sample of children who grew up in low-income communities were faced with a greater amount of physical (crowding, noise) and psychosocial stressors (violence, family turmoil) than their middleand upper-income counterparts. This study demonstrated that multiple early life stressors were often generated within stable structural contexts. Research that only looks at singular stressors as the source of dysfunction (e.g., Aseltine & Kessler, 1993; Turner, Kessler, & House, 1991), can be problematic because these studies may misattribute negative outcomes to a singular event and ignore other significant contextual events. For example, research by Aseltine and Kessler (1993) stated that marital disruption predicted increased levels of depression in a community sample but did not account for other stressful life events associated with marital disruption such as a death in the family or previous mental health issues. A publication by Turner, Kessler, and House (1991) stated that unemployment status predicted elevated levels of internalizing psychopathology compared to well-employed populations not taking into account other social factors contributing to this psychopathology. While these types of studies can be useful for studying the impacts of isolated events on mental and physical health they cannot, in isolation, provide an explanation for bad outcomes (Hammen, 1997). ELS AND PHYSIOLOGICAL STRESS REACTIVITY 6 In order to address these issues, many researchers have begun to conceptualize early life stress more holistically, by identifying and measuring diverse adversities that, when taken as a whole, contribute to a harsh or risky environment early in life. One of the most validated approaches for conceptualizing these early family environments suggests that harsh or risky family environments are characterized by high levels of conflict and aggression, as well as cold, unsupportive, and neglectful relationships (Repetti, Taylor, & Seeman, 2002). Early in life, infants and children are dependent on their environment for emotional and social nurturance (Repetti, Taylor, & Seeman, 2002). As a result, when the home environment is cold, aggressive, and/or unemotional, the child is at an increased risk for developing deficits in their ability to regulate emotion; which can later produce disruptions in psychosocial functioning (Repetti, Taylor, & Seeman, 2002; Streeck-Fisher & van der Kolk, 2000). Given the importance of assessing the complexity of the family environment for understanding an individual’s risk for emotional and physical disorder across development, the current thesis used this “risky families” framework to assess and test the impacts of ELS. The Negative Effects of ELS on Emotion Regulation Parenting style and early family environment have significant impacts on the development of emotion regulation skills in children (Chang, Schwartz, Dodge, & McBrideChang, 2003). Emotion regulation is the cognitive process of recognizing, evaluating, and subsequently monitoring and adjusting one’s emotional state to respond appropriately to situations in one’s external and internal environments (Berking & Wupperman, 2012). From infancy to early childhood, the caregiver plays a vital role in the development of emotional regulation and management skills (Taylor, Eisenberger, Saxbe, Lehman, & Lieberman, 2006), and in normal development, the child will take more responsibility for these skills over time ELS AND PHYSIOLOGICAL STRESS REACTIVITY 7 (Berking & Wupperman, 2012). However, research shows that individuals who are raised in harsh and risky environments may show deficits in emotion management and regulatory skills (Burns, Fischer, Jackson, & Harding, 2012; Taylor et al., 2004). For example, studies confirm that children who grow up in harsh family environments have shown abnormal emotional responses during stressful circumstances (Taylor et al, 2006). Abnormal stress responses further enhance the individual’s risk for emotional and behavioral problems (Repetti, Taylor, & Seeman, 2002) in adolescence and adulthood. At the current time, there are conflicting findings regarding how these abnormal stress responses manifest and present in these individuals. A study by Miller and Chen (2010), suggested that maltreated children develop a hypervigilance for cues that denote anger or threat. The children in this study showed an exaggerated emotional response to angry adult interactions that lasted well into their adult years; long after they had left the risky environment. One explanation for this finding is that trauma early in life disrupts attentional processes during stress, such that those who have experienced trauma have enhanced attention for and trouble disengaging with stressful stimuli (Marusak, Martin, Etkin, & Thomason, 2014; Tottenham et al., 2010). Additionally, a study by Shapero et al. (2014) demonstrated that emotional abuse during childhood impacted the ability of young adults to manage emotional events in their daily lives, such that those who had experienced higher levels of abuse showed heightened reactivity to adverse events. Both of these studies indicate that ELS can result in long-lasting increases in vigilance and reactivity to stressors. On the contrary, some studies have shown that people who have grown up in risky family environments show blunted responses to emotional stimuli. Research by Taylor et al. (2004) used the Risky Families Questionnai