Owen Wilson is said to be "doing well" since his stay in hospital

Wilson, 38, dropped out of the DreamWorks movie after reports of an apparent suicide attempt in August.

Ben Stiller directs and stars in the film, about a group of actors making a big-budget war movie, who are forced to become the characters they play.

Wilson, who was admitted to hospital last month, asked to be allowed to "heal in private" in a statement.

Oscar nomination

McConaughey, 37, has an uncredited cameo in the Tropic Thunder, according to his publicist.

In previous films, such as The Wedding Planner and Ed TV, he has had starring roles.

He will feature alongside Jack Black, Robert Downey Jr and Nick Nolte in the movie, which is being filmed in Hawaii.

Matthew McConaughey has an uncredited cameo in the movie

Wilson's previous hits include The Wedding Crashers, in which he and Vince Vaughn played men who show up uninvited at weddings in order to get dates.

The comedy grossed $285m (£142m) at the global box office in 2005.

Wilson, who had been dating actress Kate Hudson until recently, has also starred in Starsky and Hutch, Zoolander, and You, Me and Dupree.

He was nominated for an Oscar in 2002 for his writing work on The Royal Tenenbaums.

Last month he dropped out of the Venice premiere of his new film, The Darjeeling Limited, to recuperate at his home in California.

Film-maker Wes Anderson, said the actor was "doing well" and had been "making us laugh".