Yes, absolutely. In fact, that's part of why it's such a razor edge. Meds are useful for dealing with both types. The difference, though, is that when it's exogenous only, the meds are useful mainly to get you out of the rut, and put a floor under you, short term.
And that's no longer such a big difference. Recent studies have shown that over time, some people with endogenous depression - whether inborn or induced! - are literally HEALED by the medications. Their brain chemistry is actually CORRECTED. Which means they can also be weaned from the meds and remain stable thereafter. [edit in: should be done with a cooperative, i.e. open minded, doctor, because you may need to go back on or re-increase the dose if it's too soon, or if your particular chemistry doesn't respond this way. Many doctors just put people on meds and then 'shelve' them, mentally, so it's important to find an open minded one.]
This is also turning out to be true for PTSD, for some people.
The razor edge problem is this: in the harrowing situation, you are being fed messages - programmed not to resist, one way or another. If you are in a literal Darfur, then there is literally no escape without great risk, and virtually nothing is truly within your control. That is a true message. If you are in a domestic abuse situation, you may well be just as trapped, until you can begin to work out - at great risk - some plans for escape; but it's more like a slave trying to reach the Underground Railroad, than it is like a fed up employee with a year's salary banked as a cushion, strolling out the door with a wave of one finger, to start her own business.
These messages of entrapment and defeat are true in context; the antidote isn't to refuse to believe them, but to decide never again to be trapped in the same way. In similar future entrapments, these messages would be true again. That is why it is so important to look at them and learn from them, not only to overwrite them. You do need to be counterprogrammed, but strategically! You need to remember what the traps look like, how they smell, so that you don't just cheerful yourself right back into one. Because there are traps, and they are real.
Balance. On one side, inappropriate gloom and doom. On the other side, unrealistically rosy thinking. In the middle, a narrow but navigable valley - the path through reality, with light and dark, warmth and cold, joy and tears, and a whole real world to explore.
edit in: I know whereof I speak. I was on an SSRI for a year. Supersensitive to it, so I never went above the lowest, theoretically not effective, starter dose. Ineffective hah. My affect flatlined, and I came off it because I wanted to feel love surging through me when I held my animals in my arms [I believe they deserved to feel and smell that chemical change, it wasn't just for me]. When I titrated off entirely, lo and behold: the outlook, the awareness, was still there, and some things brought me down, but I no longer pitched a tent there and set up base camp. The induced endogenous component was gone.
