Vanderbilt University · Psychology

Identifying the environmental determinants of brain and mental health.

Twins grow up sharing their genes and a childhood — so comparing them lets us tell which of life’s experiences truly shape mental health, and which only seem to.

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What we study

How do life’s exposures shape the developing brain?

We investigate how environmental factors — socioeconomic disadvantage, toxicants, victimization, and substance use — relate to mental health, and whether those associations are causal or statistical confounding. The lab draws on developmental science, clinical psychology, behavioral genetics, and psychiatric epidemiology.

01

Causes, not correlations

Using twins and longitudinal cohorts to find the changeable mechanisms that link environmental exposures to mental health — and to separate cause from confound.

02

Built-in counterfactuals

Twins share a childhood home — and much of their DNA. When one is exposed and the other isn’t, a divergence in how their lives unfold can’t be explained by the genes or upbringing they share — directing the search toward the experiences that differ between them.

03

Rethinking “normal”

Extended monitoring shows most people meet criteria for a mental-health disorder at some point — reshaping how we think about stigma and what enduring mental health really means.

“If you stay mentally well your entire life, you’re not normal.”

Only about 1 in 6 people reach midlife having never met criteria for a mental-health disorder. Because these problems are so common, our work focuses on the environmental causes behind them — which ones raise risk, and which can be changed.

Schaefer, Aeon · Psyche (2021)

Selected publications

Recent work

2026

The lasting impact of youth bullying exposure on adult labor-market outcomes: An interdisciplinary review

Martinez, M., Hu, Q., Schaefer, J. D. · Developmental Review, 80, 101269

In press

Socioeconomic consequences of childhood ADHD: A longitudinal twin study

Mohan, A., Iacono, W. G., McGue, M., … Schaefer, J. D. · Journal of the American Academy of Child & Adolescent Psychiatry

In press

Challenges with measuring emerging mental-health symptoms during the transition to adolescence (ABCD Study)

Martinez, M., Mittal, V. A., Haase, C. M., Schaefer, J. D., Damme, K. S. · JCPP Advances

In press

Distinct ERP biomarkers of broad versus specific dimensions of the HiTOP externalizing spectrum

Patrick, C. J., Ribes-Guardiola, P., … Schaefer, J., et al. · Clinical Psychological Science

2026

Predicting externalizing symptom trajectories in National Guard recruits: The role of adverse childhood experiences

Sloan, A. F., Bron, T., Marquardt, C. A., … Schaefer, J. D. · Journal of Traumatic Stress, 39, 282-294

The Vanderbilt University Twin Research Center

A contact list of twins in the state of Tennessee who have expressed interest in participating in future twin-related research studies.

Learn about the VUTRC