The "white coat effect" does occur even for patients who are taking medication to lower their blood pressure, according to research published in the American Journal of Hypertension (February 2004). The white coat phenomenon explains why patients with high blood pressure have higher readings at the physician's office, compared with those at home.
The results are based on a study of 276 patients (138 treated patients and 138 untreated patients) who had their blood pressure taken in the physician's office, at home, and by ambulatory monitor. The researchers discovered that the untreated group tended to have a greater white coat effect, compared with the treated group. Furthermore, 27% of untreated participants had a clinically important effect, compared with 20% of treated patients.