What I have read is that antidepressants without a mood stabilizer can trigger mania/hypomania, it's not a guarantee. Some do not believe in using anti Depressants in bipolar at all because of the belief it destabilizes the cycling over the long term.

I went from severe depression to hypomania in two weeks on Zoloft. To be fair it was the only time I had sought treatment for depression...nobody knew I was bipolar!