Ryan will replace Dianne Wiest as Paul's (Byrne) therapist, according to the Boston Globe. Winger will play a washed-up actress who comes to Paul for therapy. DeHaan will play a gay teenager.
Stage and screen actor-writer Dan Futterman (Angels in America, Further Than the Furthest Thing, Oscar nominee for "Capote" screenplay) will serve as co-executive producer of this season of the series with his wife, Anya Epstein.
Ryan received Tony Award nominations for her work in A Streetcar Named Desire and Uncle Vanya. A cast member of the "Capote" film, she has also appeared on "The Wire" and in the film "Gone Baby Gone," for which she took an Oscar nomination.
Winger, an Oscar nominee for "Shadowlands," "Terms of Endearment" and "An Officer and a Gentleman," appeared Off-Broadway in The Exonerated and at Boston's American Repertory Theatre in How I Learned to Drive and Ivanov.
DeHaan has appeared Off-Broadway in Aliens, Sixty Miles to Silver Lake and End Days. The third season of "In Treatment" will begin Oct. 25 on HBO.