Quitting (2001)
Quitting is a 2001 Chinese drama film directed by Zhang Yang, starring and based on the true life story of Jia Hongsheng. Jia, an actor and former drug addict, battled his addiction to marijuana and heroin for five years from 1992 to 1997. All members of the cast, from Jia and Jia's family members right down to the doctors and patients at a mental institute Jia was admitted to, are real people playing themselves. The film premiered at the Venice Film Festival on 4 September 2001 and clinched the NETPAC Award.
More at Wikipedia.