I think our theories might be similar.

I believe that neurotransmitters and other chemicals play a role in channeling, which is why some people need gestures to open the pathways required to form a weave, and why channeling starts in early adulthood.

The Oath is like a weave of Compulsion, and that would inherently harm your brain's pathways. It interferes with the One Power and the way it works and thus interferes with the slowing process.

Maybe.