R E S E A R C H

we all experiences stress, and high doses of stress can increase our risk for illnesses like cardiovascular disease, cancer, and diabetes as well as early death. the overarching goal of the shad lab is to help reduce the health risks associated with stress and help people live their healthiest lives. To this end, we aim to answer two primary questions:
(1) how does stress get inside our bodies to alter our biology?
(2) what can help us reduce the harmful health consequences of stress?

understanding how early adversity influences physical health

Stressful experiences during childhood and/or adolescence are relatively common experiences and have been linked to a variety of health problems across the lifespan. Our work seeks to understand how early experiences of stress influences the foundation of health and affects disease risk decades later. We and others have proposed that early adversity influences health by altering brain development in ways that has implications for the way people biologically and emotionally respond to the threats and challenges that they face in their lives. In support of these ideas, we have shown that early adversity is linked to lower levels of positive emotions in everyday life, which in turn is linked to higher levels inflammation during adolescence. We are currently investigating whether this pattern persists and is evident later on in the lifespan by examining whether early adversity is linked to chronic disease burden in midlife adults through greater exposure to everyday stressors and heightened negative emotional responses to them. In another project, we are investigating the role of the brain as another pathway through which early adversity can influence physical health.

identifying who’s at risk and who’s protected against the impacts of early adversity

People differ in the way they respond to stress. This means that, thankfully, not all youth who experience adversity will go on to become sick adults. We seek to understand what increases susceptibility to the ill effects of early adversity and what buffers against them, which can help us develop interventions that are actually effective in minimizing the risk for poor health related to early adversity.

Who’s vulnerable? We propose sleep as an important factor that may potentiate the effects early adversity because sleep influences the very same psychosocial processes, biological systems, and chronic conditions that are also affected by early adversity. As such, it may be that sleep difficulties, like losing sleep or waking up frequently throughout the night, exacerbate the underlying latent risks set by early adversity. Supporting this idea, we have shown that everyday stress is linked to altered functioning of the HPA axis (a key biological stress system with relevance for physical health) only among adolescents with poor sleep (i.e., low sleep efficiency, an indicator of sleep quality), but not among adolescents who have better sleep. We have since shown this pattern for expression of inflammation-related genes in immune cells and to psychological outcomes, including negative emotions in everyday life and depressive symptoms. The next step in our work in this area is to better understand the pathways through which sleep and stress interact to influence health and whether these findings persist beyond adolescence.

Who’s protected? Having close, supportive relationships with others is linked to better health outcomes across the lifespan and can buffer people from the negative consequences of stress. This applies specifically to early adversity--that is, individuals who experiences early adversity don’t seem to show negative health outcomes if they also had supportive relationships, usually with at least one of their parents, at the time they experienced adversity. But the chronic diseases linked to early adversity tends to emerge decades later in adulthood, presumably after termination of exposure to early adversity. That means there’s an interim period of several decades, and that raises the question of whether later experiences of supportive relationships much after early adversity exposure can similarly offset the health risks set by early adversity. Our initial study aimed at addressing this question showed that social support was associated with reduced 20-year mortality risk to a greater extent in those who reported childhood abuse compared to those who reported minimal or no abuse. This suggests that later positive experiences may help decelerate the health effects associated with early adversity. Following-up on this work, we aim to identify other positive experiences after termination of exposure to early adversity that may similarly “reverse” the effects of early adversity. We are also working to understand whether the buffering effects of later positive experiences differ by developmental stage.

daily experiences of stress and health

Acute stressors—such as conflict, work deadlines, and being reprimanded by a supervisor—are pervasive and occur regularly in daily life. A second line of my research examines whether these mundane stressors have implications for physical health. It’s not likely that a single stressor or one stressful day profoundly impacts our health. But facing and dealing with acute stressors repeatedly, day after day, may accumulate to affect physical health. It may do so by altering the body’s biological response to stress. Supporting this idea, we have shown that having more negative social interactions in everyday life is associated with higher levels of inflammation, a process involved in the etiology of many chronic diseases of aging, including diabetes, cardiovascular disease, and some cancers. In a study that took a deeper dive into this connection between everyday stress and inflammation, we showed that having more stressful days in everyday life was associated with greater expression of genes governed by NF-kB (a key transcription factor that regulates inflammatory activity) in immune cells. Because these markers don’t reflect actual disease or disability, we’ve also shown that these patterns extend to a clinically important outcome, mortality. We found that greater exposure to stress in everyday life as well as people’s emotional responses to them were associated with greater mortality risk. Together, these studies dispel the notion that only major stressors have ramifications for physical health and suggest that mundane stressors in everyday life can also have health consequences.