During the depressingly somber I Smile Back, Sarah Silverman's Laney Brooks stands in front of a mirror examining her face and naked breasts. It's a signature moment in which an actress known for comedy makes it amply clear that she's creating a character who's distressingly aware that time is the enemy of the firmness of youth. Based on a 2009 novel by Amy Koppelman, I Smile Back proves relentlessly depressing as Laney dips into drugs, paranoia, infidelity and despair. As the mother of two, Laney is losing her grip. Her husband (Josh Charles) doesn't know what to do, other than to encourage her when she commits to yet another session of rehab. The movie gives Laney daddy issues -- Chris Sarandon makes a brief appearance as the father Laney never really knew -- but director Adam Salky never convinces us that I Smile Back is anything more than a horrifying wallow in bad behavior built around Silverman's brave performance. I have nothing against watching characters in movies suffer, and I don't mind suffering along with them, but in this case I had trouble differentiating between a suffering character and an actress who seemed to be pushed into one demeaning situation after another.