But the British-born Mr Sullivan, 32, said his decision to quit one of the most coveted posts in American journalism was unconnected to his illness. "This is not stepping down because I'm sick and going away and dying," he told the Washington Post.
There are suggestions, however, that he might not have jumped, but that the magazine's owner, Martin Peretz, might have pushed him out.
It has been an open secret in media circles for some time that Mr Sullivan's five years in the editor's seat at the New Republic have been marked by a great deal of internal bickering. The chief complaint was that he had driven the influential non-partisan magazine downmarket, that under his reign it had ceased to carry the clout it had in Washington during the Eighties. The New Republic literary editor, Leon Wieseltier, showed no mercy for Mr Sullivan. He told the Washington Post: "The problems around this office were not medical problems. He was responsible for an extraordinary amount of professional and personal unhappiness. In his little farewell address he said he feels unburdened. Well, he's not alone."
The moment of deepest unhappiness perhaps came in 1994 when Mr Sullivan decided prominently to publish an adaptation from The Bell Curve, a highly controversial right wing book that sought to draw a biological connection between race and intelligence. Faced with an office insurrection, he agreed the next week to publish 19 articles, some by his own staff, harshly critical of the book's conclusions.
Mr Sullivan's reputation inside the magazine never recovered and in recent weeks the feeling has grown that his judgement was failing him. An article by Camille Paglia, psychosexual in its analysis, on Hillary Clinton which ran under the title "Ice Queen/Drag Queen" drew outraged letters from readers, many of whom announced they were cancelling their subscriptions.Reuse content