Sympathetic Nervous Reactivity in Sexual Minority Health Disparities

Despite increasing levels of societal acceptance towards same-sex partnerships, sexual minority (SM) individuals (lesbian, gay, and bisexual individuals) experience excessive personal and institutional discrimination across a variety of contexts. A 2017 national survey found that more than half of lesbian, gay, bisexual, transgender, and queer (LGBTQ) respondents reported that they or an LGBTQ friend or family member had been threatened or non-sexually harassed (57%), sexually harassed (51%), or experienced violence (51%) based on their gender identity or sexual orientation. A considerable proportion of respondents reported personally experiencing slurs (48%) and insensitive or offensive comments or negative assumptions (40%) based on their sexual orientation alone (Harvard T.

H. Chan School of Public Health, 2017).

In addition to facing outright prejudice and interpersonal violence, sexual minorities, like other stigmatized groups, inhabit a structurally vulnerable position in society, facing greater challenges in seeking and receiving support, protection, and fair treatment from institutions (Hatzenbuehler, 2016). For example, less than half of U.S. territories possess laws addressing hate crimes, employment discrimination, or housing discrimination based on sexual orientation (Human Rights Campaign, 2018). Studies have also found higher rates of unmet medical needs among sexual minorities (Baptiste-Roberts, Oranuba, Werts, & Edwards, 2017; Luk, Gilman, Haynie, & Simons-Morton, 2017).

In addition to the aforementioned disadvantages, sexual minorities experience poorer mental health than their heterosexual counterparts. An extensive body of literature has found elevated rates of poly-substance, alcohol, and tobacco use; depression and anxiety disorders; stress-related disorders including PTSD; disordered eating; and suicide risk across the lifespan (Baptiste-Roberts, Oranuba, Werts, & Edwards, 2017; Cochran, Balsam, Flentje, Malte, & Simpson, 2013; Hatzenbuehler, 2009; Mays & Cochran, 2001, Meyer, 2003).

The Minority Stress Model, a conceptual framework for investigating and understanding health disparities, proposes that stigmatized groups’ disproportionate exposure to stigma-related stress (“minority stress”) results in the aforementioned health disparities (Meyer, 2003). Researchers working under this framework have aimed to explain inter-individual health differences within stigmatized populations by identifying the pathways through which stress exposure translates into negative health outcomes (Hatzenbuehler, 2009; Lick, Durso, & Johnson, 2013), while also examining factors that may promote resilience in these populations (Fredriksen-Goldsen, Kim, Bryan, Shiu, & Emlet, 2017).

Despite the well-established link between psychological stress and physical health, and the aforementioned literature recognizing sexual minorities’ disproportionate exposure to minority stress, literature on SM physical health disparities is lacking and narrow in focus, with the majority concentrating on HIV, STIs, and sexual health for gay men (Dyar et al., 2019; Lick, Durso, & Johnson, 2013; Brennan, Bauer, Bradley, & Tran, 2017). Furthermore, many of the physical and mental health consequences of chronic and acute stress overlap with health disparities experienced by SM individuals, including but not limited to: PTSD and other stress-related disorders, cardiovascular disease, infectious disease, depression, and anxiety disorders.

In a review on SM physical health disparities, Lick, Durso, & Johnson (2013) assert that SM health research would benefit from drawing upon findings in the stress literature. In particular, they recommend that future studies investigate whether stress-induced physiological processes commonly known to drive adverse health outcomes in the general population also apply to the unique and varied minority stressors and health outcomes experienced by SM individuals.

This paper will first provide an overview of the physiological stress response and studies that examine the physiological process that may drive health disparities in SM individuals—dysregulation of the sympathetic nervous system (SNS).

The Physiological Stress Response: An Overview

The stress response serves the immediate purpose of mobilizing and shifting an organism’s attention and resources towards coping with the stressor (McIntyre, 2012). The fast-acting sympathetic portion of the autonomic nervous system (ANS) and slower-acting hypothalamic-pituitary-adrenal (HPA) axis initiate the production of stress hormones, catecholamines and glucocorticoids, respectively, producing the somatic experience of arousal, characterized by elevated heart rate, increased blood pressure, dilated pupils, and a hypervigilant state (Schwabe, 2011; Finsterwald, 2014). Once the stressor subsides, the ANS, HPA Axis, and immune system provide inhibitory feedback to one another to prevent hyperactivity and return the body to homeostasis (Oken, Chamine, & Wakeland, 2015). Catecholamine levels are typically the first to respond, recovering to baseline levels within minutes, while circulating glucocorticoids continue to act, consolidating newly-acquired emotionally arousing memories that provide information pertinent to survival. Thus, stress can be viewed as an adaptive physiological response that prepares organisms physically in the moment and promotes learning on a synaptic level long after the stressor occurs (Schwabe, 2011; Finsterwald, 2014; McIntyre, 2012; Roozendaal, 2009, Phelps, 2005).

However, when stress levels are chronic, frequent, or severe, stress loses its adaptive function. High levels of stress are associated with a number of consequences, including an alteration of brain functioning, a dysregulation of the nervous and immune systems, physical disease, and psychological sequelae (Finsterwald, 2014; Oken, Chamine, & Wakeland, 2015; Roozendaal, 2009; Schneiderman, Ironson, & Siegel, 2005).

Studies of ANS Dysregulation in Minority Stress

Sympathetic Reactivity and Health

Sympathetic reactivity is associated with exposure to social stress and hypervigilance. Traditionally, scientists have measured sympathetic nervous system (SNS) activity via the measurement of bodily symptoms associated with arousal, including heart rate, blood pressure, and electrodermal activity. More recently, investigators have identified salivary alpha amylase (SAA) as a non-invasive biomarker for SNS activity. SNS reactivity may present as elevated SAA output throughout the day, heightened blood pressure, heart rate reactivity, and poor recovery in response to experimental stressors (Oken, Chamine, & Wakeland, 2015; Yoon & Weierich, 2016). Chronic stress exposure and the concomitant frequent cardiovascular responses may play a role in the development of downstream cardiovascular diseases associated with SNS reactivity, such as hypertension and atherosclerosis (Sawyer, Major, Casad, Townsend, & Mendes, 2012).

Sympathetic Reactivity and SM Stress

In the Minority Stress Model, proximal stressors are internal processes that occur following exposure to external stressors, such as discrimination. They are thought to mediate the relationship between discrimination and health outcomes. Rejection sensitivity and concealment of sexual identity are two such processes pertinent to SM individuals (Meyer, 2003). Rejection sensitivity is associated with victimization and is characterized as an experience of anxiety and humiliation in response to actual or perceived social rejection. This may manifest as hypervigilance towards threatening cues (Ehrlich, Gerson, Vanderwert, Cannon, & Fox, 2015; Feinstein, Goldfried, & Davila, 2012). To protect themselves from stigma, SM individuals may choose to conceal their sexual identity. However, the decision to do so may result in social anxiety, isolation, and rumination in SM individuals (Meyer, 2003). Thus, both of these proximal stressors manifest in similar ways to SNS reactivity in general populations.

Few studies have investigated SNS reactivity as a physiological pathway between SM stress and health. To date, most of the literature on SNS reactivity and minority stress has focused on the relationship between cardiovascular risk and perception of discrimination among ethnic minority populations (Sawyer, Major, Casad, Townsend, & Mendes, 2012; Williams & Mohammed, 2009). As reviewed by Lick, et al. (2013), Pérez-Benítez, et al. (2007) found a striking relationship between cardiovascular reactivity and sexual orientation concealment among a sample of healthy gay men: men who concealed their orientation on a daily basis but disclosed it in the experimental task showed the greatest cardiovascular recovery. More recently, Austin, et al. (2018) found significant differences in diurnal SAA patterns between sexual minority and heterosexual young adult women. The study measured recent trauma exposure (within past 30 days) and potential confounding variables known to skew SAA readings (sleep quality and duration, mood, medications, hormonal contraception) via questionnaires administered on the day of saliva collection. Saliva was collected at four time periods to obtain a complete picture of diurnal patterns. According to the Minority Stress Model, Austin, et al. (2018) predicted that sexual orientation would result in a blunted SAA awakening response and an elevated output throughout the day for young men and females in the study. However, they only found significant differences in SAA diurnal rhythms among women. Furthermore, they found no relationship between sexual orientation and recent stressful life events. Austin, et al. (2018) conjectured that unmeasured differences in childhood trauma exposure, attachment style, and higher levels of chronic stressors may have accounted for this unexpected outcome. Although not mentioned by the authors, these results may reflect on the instruments used to assess stress exposure in minority populations. That is, experiences of discrimination, which are chronic and daily, despite not meeting the criteria of a "stressful life event," may exert lasting physiological effects. Additionally, this study provides a starting point for future studies in examining how differences in chronic exposure to discrimination affect SNS activity in SM populations.

Conclusion

Despite the large number of studies examining SM health disparities, questions remain. Advancing research in this area, in part, relies on understanding the mechanisms by which physiological stress processes link minority stressors and health outcomes. While recognizing the need to investigate SM disparities, the experience of discrimination is complex; there is no “one size fits all.” Accordingly, research that sheds light on interindividual differences is needed. Studies that measure biomarkers of stress along with degree, type, and duration of minority stress exposure hold the promise of providing a more individualistic understanding of the mind-body connection in minority stress-driven health disparities.

Research on minority stress and health disparities is critical because discrimination and health disparities persist. Advancing science in this area will support the initiatives of policymakers, activists, and educators who aim to promote equality and inform healthcare providers who wish to provide culturally-sensitive, adequate, and preventative healthcare to vulnerable populations, while validating the physical and emotional experience of minority stress.

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