RJ:
Access to the True Power is a matter of wanting it and the Dark One letting you. NOT black cords. In the Prologue to The Eye of the World we saw True Power used to heal insanity. The One Power cannot be used to heal insanity. True Power used at Shayol Ghul will fry you instantly

And:

We've read in the Forsaken's POVs that channeling in the Pit of Doom would have some...unpleasant...effects. Is this related to the nature of the opposition of the One Power to the True Power or is it the Dark One consciously acting against the channeler? If so, why should the Dark One care?
Robert Jordan
It is a matter of the Dark One consciously acting, though interactions between the One Power and him, the source of the True Power, can be unpredictable.

From Sanderson, clarifying the apparent contradictions of RJ (perhaps caused by bad reporting of what he actually said):

There may be a tad more to the cords that RJ didn't state, but I will say that one major reason is the taint protection.

(Note: he need not have confirmed it anyway. Rand cut Asmodean's Black Cords, and Jordan once gave an elaborate answer that no one but perhaps a Forsaken (but no one else) know how to sever the ability to use the True Power, and that it can't be done with the OP. In short, the Black Cords are definitely not the conduit to the True Power. They're related to the DO's protection against the taint, which is why we've seen them only on male channellers and not Lanfear. Rand never had this protection, so no black cords. )

RJ:

No one can tell if you're using the True Power except the Dark One, of course.
You must be a stone cold fanatic to want to use the True Power.
Can Moridin use a male angreal if he channels the True Power?
Robert Jordan:
No.


And is it addictive?
ROBERT JORDAN
Yes.
QUESTION
Entirely.
ROBERT JORDAN
So is the One Power. That's one of the things that I intended from the beginning. The One Power has at least the potential for good, and it is something used by those on the side of good.

(Note: in RJ's mind, it means the True Power doesn't have the potential for good, while the One Power at least has it. Very important theme for him.)