I was first diagnosed with depression and put on an SSRI, and for a while that really seemed to do the trick. I was feeling pretty great. Then the antidepressant just stopped working. I went back to my GP and was referred to a psychiatrist, where I was properly assessed and diagnosed. Realised the "feeling great" part was hypomania caused by the SSRI, which was obviously followed by depression.
So for me, a mood stabiliser has been necessary. I have been on Lamictal for almost two years now. Before that I was on quetiapine (Seroquel) for three years, for reasons unknown to man since my main problem has always been depression. I gained 50 pounds and felt like my brain had been replaced by a block of cement, so eventually I just decided that I couldn't be on it anymore. Once I switched to Lamictal I lost all the weight I had gained over three years in just six months, and I feel much better now than I did on quetiapine (or "satan in pill form" as I like to call it).
I recently went from taking 150mg of Lamictal once a day to taking the same dose twice a day due to another depressive episode. So far my mood seems to be improving, but I think it has made my migraines worse.

Waiting to find out if it's just a phase or if I need to look into other alternatives, as I simply cannot have two or three migraines per week. It's exhausting.
I hope you find something that works for you!