I love the Lord, just to establish that I'm aware Christians try to justify mental retardation as some weird "blessing".
No it's pretty clear to me that these sorts of things are part of that fallen state. A verse Ive heard quoted is this one;
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John 9:1-3
9 And as Jesus passed by, he saw a man which was blind from his birth.
2 And his disciples asked him, saying, Master, who did sin, this man, or his parents, that he was born blind?
3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.
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And even in this case, it's the last part there. Is medicine and a cure not considered the works of God who is good? Wouldn't being able to cure or prevent this shit be a miracle?
TL;DR religious/faith based justifications for this sort of thing irk me. Sorry for sperging. Carry on all