Lancet surveys of Iraq War casualties
The Lancet, one of the oldest scientific medical journals in the world, published two peer-reviewed studies on the effect of the 2003 invasion of Iraq and subsequent occupation on the Iraqi mortality rate. The first was published in 2004; the second (by many of the same authors) in 2006.
Source: Wikipedia — Lancet surveys of Iraq War casualties (CC BY-SA 4.0)