Placebo does not lower ambulatory blood pressure.

Abstract
The effects of 4 weeks of placebo on clinic and on ambulatory blood pressure, measured non‐invasively using the Remler M 2000 portometer, were studied in 46 hypertensive patients who were included in three consecutive double‐blind randomized placebo‐controlled trials with antihypertensive drugs. Placebo significantly reduced clinic blood pressure, but had no significant effect on ambulatory blood pressure.