ABC News has confirmed that, of those deaths [of U.S. troops] in Iraq, at least five are suspected suicides. These are figures we've been trying to get for several days now, something the Pentagon really does not want to talk about.

--Martha Raddatz on this evening's broadcast of ABC's World News Tonight (text not available online)

I should acknowledge, though, that I don't know how unusual this is in war, or among populations of (mostly) young men with ready access to guns.