A new analysis of prescription rates of 600 commonly-used drugs across the United States reveals influences of racial composition, state-level health care laws, and wealth on prescription choices. The study, published October 9 in Nature Communications, also shows that some regions consistently prefer more expensive drugs, even when they have not been proven more effective than cheaper alternatives.

The United States is socially and culturally heterogeneous, with significant disparities and inequality in health metrics such as life expectancy. However, it’s not clear to what extent these disparities extend to health care.

Andrey Rzhetsky, PhD, the Edna K. Papazian Professor of Medicine and Human Genetics at the University of Chicago and postdoctoral scholar Rachel Melamed, PhD, used medical claims data from over 150 million patients in more than 2,000 counties across the U.S. to compare the prescription rates of 600 commonly-used drugs, including opioids, antidepressants, anti-inflammatories and hypertension medications.