No, it's not necessary. I'm not depressed, but I have had some suicidal episodes lately. I have been depressed in the past, so I know what that feels like, and my current state of mind is definitely not depressed.
There is some depressive symptoms that overlap with my current state of mind I guess, and combined with the suicidal ideation, even I myself thought for a minute that I must be depressed, despite my moods not fitting that label at all. But no, hanging out here, observing the mental state of some people here who are clearly depressed, it is obvious to me now that I am not. I recognize what people are going through here from my past depression, and I recognize that I'm not in that place right now.
However, I do see that the mental and behavioral patterns in me right now which drive my suicidal ideation, are potentially (if I allow it) the precursors of depression. It's like I'm suicidal in anticipation - feeling like "if this is how it's going to be, I might as well ctb, before I reach that depressive state".
Honestly, recognizing that is a big deal to me right now. It means that the therapy and all the inner work of the past 10 years have not been for nothing. It means I have gained the awareness that will allow me to at least attempt to correct my direction before it is too late, and hopefully avert crashing down that black hole again...