I don't think it really is. Stop and think: firstly to use Sadin you must battle with it rather then let it envelop you like Saidar. Is this evough to drive some people mad after a while? I think it could. The madness of the hundred companions could have been caused mearly on those hundred male Aes Sedai, but when the women saw it feared it had effected all of them. El Ratoncito Gris pointed out that the woman don't turn mad, but the are growing lesser. This may be caused by many things. for example before the War of the Shadow, who did the Aes Sedai marry? I'd guess other Aes Sedai. This would cause power to be strengthened in children because both sides of the power were in the parents.