Our mullein study

The study is not open yet. It opens only after an independent ethics board approves the plan, and the plan is registered publicly before anyone joins. This page will say when.

The question

In adults who smoke daily and have a long-lasting cough, does four weeks of mullein improve cough compared with an identical-looking placebo?

How it works

• Two four-week periods with a two-week break between: mullein capsules in one, placebo in the other, in random order. Nobody — including us — knows which is which until the end.
• Cough is measured with the Leicester Cough Questionnaire, a standard tool used in cough research.
• A short daily cough diary, and cigarettes per day — so the study would also notice if taking a supplement made anyone smoke more.

Who it’s for

Adults 21 and over who smoke cigarettes daily and have had a cough for two months or more. People with a diagnosed lung disease, who are pregnant, or who cough up blood should talk to their doctor instead.

Help to stop

Everyone who joins gets quit-smoking support, and stopping during the study is welcome. Free help to stop smoking: smokefree.gov · 1-800-QUIT-NOW (1-800-784-8669).

Fixed before it starts

The plan, the measure and the analysis are fixed and published before the study starts, so the result cannot be shaped after the fact.