Preston et al1 confirm the substantial effects of placebo on both blood pressure and adverse-event reporting. However, there are at least 3 reasons to question their conclusion that these facts warrant the continued use of placebo controls in trials of antihypertensive therapies for stage 1 and stage 2 hypertension.
First, the much higher rate of patients exceeding the blood pressure safety limits in the placebo group1 is cause for concern. Though the rates of serious complications were similar during the year-long trial, this does not mean the longer-term consequences of such uncontrolled hypertension will be similarly benign. The long-term consequences of relatively short periods of uncontrolled hypertension have yet to be fully elucidated, but they are unlikely to be negligible. In recognition of this, the Food and Drug Administration has considered it safe to give patients with hypertension placebo for "4-8 weeks"2 or the "short term"3 in randomized controlled trials of antihypertensive agents, not for a full year as Preston et al did.
Halpern SD, Karlawish JHT. Placebo-Controlled Trials Are Unethical in Clinical Hypertension Research. Arch Intern Med. 2000;160(20):3167–3168. doi: