From molecules to mental health

ASU professor studies how stress can change children's gene expression and, later, behavior


Portrait of ASU Assistant Professor Candace Lewis.

Candace Lewis, assistant professor in the School of Life Sciences and Department of Psychology at Arizona State University.

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How children grow up affects their gene expression, microbiomes and behavior, and as such, parenting style can have molecular consequences in children’s bodies.

For example, low household income and parent education levels are associated with children having less diversity in their microbiomes, which has been linked to future health or behavioral problems.  

Candace Lewis, assistant professor in the School of Life Sciences and Department of Psychology at Arizona State University, studies the impact of our social environments on molecules, all the way up to the brain and behavior, with the goal of making healthier childhoods for everyone. 

“I study how social experiences have the ability to shape us at the epigenetic levels in a way that influences the brain structure and functioning underlying mental health,” she said. “My research zooms in and zooms out, going from genomics to brain structure and function, and also behavior, because the entire pathway of how experiences can modify our biology, and downstream behavior is important for well-being and understanding disorders.” 

Molecular consequences of harsh parenting

Experiences change how genes are expressed through a process called epigenetics. Though physical abuse or neglect early in life is known to alter gene function, Lewis wondered whether less severe forms of trauma experienced early in life also had epigenetic costs.

She and her collaborators recently published a study on epigenetic and physiological effects of harsh parenting practices on children. 

Harsh parenting practices, which included spanking for discipline, were reported by parents when their children were 2.5 years old. Six years later, when the children were 8.5 years old, the research team identified epigenetic changes to genes involved in the body’s physiological response to stress, including release patterns of the stress hormone cortisol.  

The identified epigenetic and physiological changes in response to prior harsh parenting are a possible pathway to future problems such as stress dysregulation and mental health disorders. Lewis emphasized that just because a pathway to a pathology has been identified, it does not mean children will go down that path and end up with a disorder.

“I don’t want parents to fear that every little thing they do is messing their kids up; kids are resilient and adaptable. Parenting is a modifiable behavior, and we as a society need to recognize what we can do to support caregivers in dealing with the stressors they experience,” Lewis said.

Family resources and children’s microbiome

The makeup of the gut microbiome is thought to affect brain health — influencing moods, how people respond to stress and even how they think. In a recent study, Lewis and her collaborators examined the microbiomes of infants and children and how they were affected by their environment. 

The family’s socioeconomic status, which includes household income and parent education levels and jobs, was associated with the diversity of bacteria in individual children’s gut microbiomes. 

“Socioeconomic status is a modifiable factor that has been associated with a whole host of mental health outcomes, including cognitive, emotional and physical health,” Lewis said. 

Currently, Lewis is investigating the possibility that the types and amounts of bacteria in the microbiome may influence the health of the human body through epigenetic changes.

First-generation student, Truman Scholar and Fulbright winner

Lewis worked full time while attending the University of Alaska Anchorage as a first-generation college student. Being named a Truman Scholar put her on the path to graduate school.

“I grew up in rural Alaska and didn’t know how to navigate the landscape of higher education. Many mentors took me under their wings and helped me get through the Truman Scholar application process; I still think it’s really crazy that I got it. I was up against students who had every advantage I didn’t,” Lewis said. “It’s important to me to advocate for first-generation students to be competitive for these prestigious awards; I wouldn’t be where I am today without it.”

While figuring out what went into earning a doctoral degree, Lewis worked in a behavioral lab where she fell in love with research.

Lewis earned her PhD in behavioral neuroscience from the ASU Department of Psychology in Professor Foster Olive’s lab. Her doctoral research examined how early experiences increase vulnerability to addiction. Lewis identified epigenetic markers of stress experienced early in life that increased drug intake in an animal model. She was also able to reverse the epigenetic markers in the model, which reduced drug intake behavior.

After graduate school, Lewis decided to expand her research on epigenetics into humans. She won a Fulbright Fellowship and a Bisgrove Scholars Award from the Science Foundation Arizona. She went to Switzerland on the Fulbright first, to use neuroimaging to study the beneficial effects of psychedelics, and then worked as a Bisgrove Fellow at TGen to study the effects of early life experiences on epigenetics using twins. Lewis is currently combining these two research questions by investigating if psychedelic-assisted therapy leads to symptom reduction through epigenetic processes. 

“I enjoy the process of science and am proud that I am doing the research that I want to do,” Lewis said. “For me, my life outside of the lab is just as important to my scientific success as anything I do in the lab. Having fun, enjoying my relationships, being in nature, dancing and live music, and adventures are crucial for cultivating the creative thinking that underlies exciting science.”

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