That's a recurring thing in Deus Ex: Human Revolution. Outside of the protagonist, most people need a costly antirejection drug for the augmentations that they're societally pressured to have. Because they're otherwise uncompetitive in their work.
Reduced to a life of just using a crowbar and not talking t anyone.
But all jokes aside, it could be brain damage, but drug addiction might be a better analogy. It could be something that takes time for neuroplasticity to repair or correct.