In fact, abolition makes those negative effects more likely to occur in a well run school because the biggest single defence you have against children being harmed is the ability of decent teachers to target exactly what the child needs.
Not every negative experience is dramatic, and not every negative effect of corporal punishment is dramatic either. Many keep quiet about negative experiences because of social pressures. Where corporal punishment is widely accepted, no one wants the label of whiner or pussy or wimp. I expect that many of the negative effects are subtle and go unnoticed. People become good at hiding scars, especially when they suspect that revealing the scars will bring down, not sympathy or understanding, but derision. Probably a lot of people hide the scars from themselves.