An AP may not be effective as a monotherapy for depression. The usual recommendation is to combine an AP with an SSRI or other antidepressant, and the combo will work much better than the antidepressant or AP alone.
SSRI's are the first-line depression treatment, and sometimes require some trial and error, as different people respond differently to different ones. And it takes some patience because each one requires 3 to 4 weeks before they are completely effective.