Professor Marissa King mapped the geographic patterns of the use of antidepressants, antipsychotics, and stimulants across the United States. She identified large regional clusters, centered on Tennessee, where use of these drug classes were elevated.
In a large area of the South centered on Tennessee, use of antidepressant, antipsychotic, and stimulant medications is 40% higher than in the rest of the United States, according to a Yale School of Management study.
The study analyzed geographic differences in the use of these three classes of mental health medications using data that covers 60% of prescriptions written in the U.S. in 2008. It is the first study to examine local and regional patterns of use, which the authors mapped based on the three-digit zip code of the prescribing physician.
"We identified clear regional clusters where the use of antidepressants, antipsychotics, and stimulants was elevated," said Marissa King, assistant professor of organizational behavior at the Yale School of Management. "The geography of the cluster for each class of medication was different, but they overlapped each other, with Tennessee as the center point."
People living within one of these clusters were 77% more likely to fill a stimulant prescription, 46% more likely to fill an antidepressant prescription, and 42% more likely to fill an antipsychotic prescription than residents outside of the cluster.
King and co-author Connor Essick, a graduate of the Yale School of Public Health, found that the use of mental health medications varied considerably at the local level. For all three classes of medications, use was lowest in the western part of the country. Stimulant use, in particular, had very little penetration in the West.
King and Essick identified local extremes in medication use. Cape Cod, Massachusetts had the highest use of stimulants at 16% of residents, compared to a mean of 2.6% of the population nationally. Antidepressant use was highest in Alexandria, Virginia where two in five residents received an antidepressant, compared to a mean of 10.4% nationally. Gainesville, Florida had the highest use of antipsychotics at a rate of 4.6% of residents, compared to a mean of 0.8% nationally.
Much of the geographic variation in medication use can be explained by access to healthcare and pharmaceutical marketing efforts, according to the authors' analysis. For all three classes of medications, use rates were significantly associated with local access to healthcare as measured by the density per capita of physicians in the area, and with the amount of pharmaceutical marketing dollars paid to physicians. Stimulants were the only class of medication for which use rates were explained by the underlying prevalence, with use associated with ADHD prevalence at the state level.
"The geographic patterns we identify are striking and map onto the patterns found for a host of other medical conditions and treatments—from cognitive decline to bypass surgery. Our work suggests that access to clinical care and pharmaceutical marketing may be critical for understanding who gets treated and how they get treated," said King.
"The Geography of Antidepressant, Antipsychotic, and Stimulant Utilization in the United States" is forthcoming in the journal Health & Place.
Geographical Variation and Cluster Maps (click image for larger view)