If you have major depressive disorder, then you do not suffer from mania. You could actually have bipolar, or you could suffer from both bipolar and major depressive disorder. But a lot more than talking to o much would be have to be present to indicate that, most people do feel more talkative at some times than others. Plus people get nervous when stressed and some react to the nervousness by talking more. However if you feel that you may suffer mania too, talk to your dr and/or therapist about this concern.
And yes stress can be as powerful a trigger for both depression and mania as other factors.