November 18, 2019

Dr. Daniel Westreich

Dr. Daniel Westreich

Daniel Westreich, PhD, associate professor of epidemiology at the UNC Gillings School of Global Public Health, has authored a new textbook for first-year graduate and advanced undergraduate students in the fields of epidemiology and public health. Epidemiology by Design: A Causal Approach to the Health Sciences, published in November by Oxford University Press, is an introductory text that explores the foundations of epidemiology through the lens of causal inference – the science and philosophy that addresses understanding the differences between correlation and causation, particularly when evidence from randomized trials cannot be relied upon.

Causal inference has long been thought to be at the heart of epidemiology and public health research. It helps identify opportunities for health interventions, shape public health policy, and determine how to increase or decrease exposure to certain beneficial or harmful agents in order to improve health.

In a study published in 2016, Westreich led a team of researchers in proposing a framework for a causal approach to epidemiological studies that could provide more useful evidence in public health decision-making. That framework includes consideration of:

  • Internal validity – the confidence that there is a cause-and-effect relationship between a variable and an outcome in the study data;
  • External validity – the question of how applicable that cause-and-effect are in the real-world population for whom you want to make health policy, and;
  • Population intervention impact – understanding how the effects of exposures (like smoking) can differ from the effects of scaled-up, real-world interventions to affect those exposures (like cognitive behavioral therapy for smoking cessation).

Westreich’s new book is the first introductory textbook that frames fundamental, first-semester epidemiologic methods through a modern causal inference lens.

“The study of epidemiology is, to a large extent, about learning to ask good questions in population health,” Westreich states in the overview of the text.

Through the analysis of study designs that apply a causal approach, Westreich’s goal in Epidemiology by Design is to arm students new to epidemiology with the tools to ask better questions that will produce more relevant data and ultimately improve public health outcomes.

“I’m excited to share this textbook with students as well as anyone who wants to reexamine the fundamental methods of epidemiology through a causal lens,” said Westreich, adding that he is “grateful to all the folks who helped me create this book, especially my own teachers and the many people who peer-reviewed the work in progress.”

Westreich’s body of research applies causal inference to epidemiology and implementation science, specifically at the intersection of HIV and women’s reproductive health. His work on the book was funded by a DP2 New Innovator award from the National Institutes of Health.

Contact the Gillings School of Global Public Health communications team at

Visit our communications and marketing team page.
Contact with any media inquiries or general questions.

Communications and Marketing Office
125 Rosenau Hall
CB #7400
135 Dauer Drive
Chapel Hill, NC 27599-7400