So, as it seems people who suffer from schizoeffective disorder, have similar brain anatomy traits,
(think disordered thought, other cognitive issues and inteligence issues)

it would seem possible that the extra terrestrials, pick people to be schizophrenic suffering
and even at an early age before showing symptoms, they might do two things:

1. They "negatively" augment the brain so damage occurs

2. They start continuely negatively augmenting the brain