A doctor’s presence during a blood pressure reading triggers a “fight or flight” response that can affect the results, say researchers who studied the effect by measuring nerve activity.
“White coat hypertension” – the phenomenon when blood pressure rises in some people who are measured by a medical professional – has been known about for decades. It occurs in about a third of people with high blood pressure.

In a small study published in the American Heart Association Journal Hypertension(link opens in new window), Italian researchers examined the effect’s roots by measuring blood pressure, heart rate and nerve traffic in the skin and muscles with and without a doctor present.
The researchers found a “drastic reduction” in the body’s alarm response when a doctor was not present, said co-lead author Dr. Guido Grassi, professor of internal medicine at the University of Milano-Bicocca in Milan.