If you have an emotionally abusive partner, and don't do something about it, perhaps depression is acting as a prompt for you to take action. Some part of you (your soul, say) knows better, and via pain (depression) is trying to shift you towards a better, more joyful, result. I believe we have an innate guiding system, and that this is how it works - move away from pain, towards joy.
You can fail to take action, you can take drugs to manage the negative situation more comfortably, but, if abuse is the underlying issue, a genuine change of circumstances is required.
It is important to listen to your body and mind, and for sure - make changes when things are bad. Staying with abusive partners is not worth it.
However it can take a while to realize the problems and manage to get out. This may have effects that last for a good while.
People do not deserve abuse or the negative effects of such abuse, just because they technically could have made a change, or made it earlier.