Cheer up, Elizabeth Wurtzel! The adaptation of your 1994 best-selling depression memoir, Prozac Nation, will finally see the light of day . . . just not at the multiplex. After sitting on the shelf for more than four years (blame rumored poor test-screening scores), Miramax's $9 million movie will debut next month on cable net Starz! ''It's a good film,'' maintains Starz! senior VP of programming Stephan Shelanski, who nonetheless notes that Prozac's ''difficult'' subject matter (with Christina Ricci as the pill-popping Wurtzel and Jessica Lange as her manipulative mom) ''may have had a hard time attracting people to theaters.'' And he's done the math: ''Starz! is in 15 million homes, so if the movie reaches 20 percent of our viewers, that's 3 million right there.'' Miramax, which plans to release Nation on DVD eventually, called the reported $900,000 deal ''a great way for a larger audience to see the film.'' Funny: We call it cutting your losses.