To what extent is Eugene O'Neill's The Iceman Cometh autobiographical?

The setting of the play, Harry Hope's saloon, was taken from
O'Neill's own attendance of Jimmy-the-Priest's saloon and rooming house in the early 1910s.
O'Neill wrote the play in the last years of his life and The Iceman Cometh
is haunted by the same sense of death and despair that characterized the last part of
the playwright's life. To some critics, the play reflects the author's struggles with alcholism
and his disordered youth. It builds directly on O'Neill's encounters at Jimmy-the-Priest's and
the sense of hopelessness and being failed by the American Dream that these showed. The dive was
also the place where O'Neill attempted suicide in 1912.

In addition,
the character of Hickey appears to have much in common with O'Neill's older brother James, who
had proved a disappointment for Eugene. The third links below takes you to a comprehensive
New York Times article that reconstructs all the autobiographical elements
of the play. However, not all critics believe that the play can be read as an autobiography of
the author. See, for example, Eugene O'Neill's Last Plays: Separating Art from
Autobiography. By Doris Alexander. Athens: University of Georgia
Press.