Dragons and Madness

[Lucia Targaryen]

Is it possible that dragons abated inbred madness?

Looking at a family tree, the Targaryens were much more inbred pre-Dance but madness really only started after the Dance ie. Baelor's excessive piety, Rhaegel dancing naked in the Red Keep, Aerion Brightflame, and of course Aerys II whose parents were siblings but then you have to go back to his great-great-great grand parents (Aegon IV and Naerys) for a brother-sister marriage. 

Of course there's Maegor but he seems to have been conceived with black magic and didn't bond with Balerion until he was an adult.

Then there's Old Valyria. We are told that incestuous marriages were most common amongst the dragonlords and that the Freehold existed for 5,000 years. Would Valyria have lasted so long if a bunch of insane dragonriders were around? I highly doubt it. 

Ergo, my theory is that the magic of dragons held back the insanity of inbreeding. 

[Moiraine Sedai]

Maybe.  Males were much, much more prone to madness.  The dragon bond likely prevented madness.  After all, Valyria could not have accomplished what she did if the ruling families had a high incidence of madness.

[Euron III Greyjoy]

Further evidence for dragons having a good effect on the Targaryens, for the first few years of his life, Aenys was weak and sickly, until he hatched his dragon. 

[Marcelowww]

That theory makes sense. Maybe that's the reason why Daenerys has not gone crazy yet.