Yeah, Masema went starkers because Rand was calling up Heroes from the Horn (close enough, since he wasn't present when it was blown), fighting the Dark One in the sky above him, and otherwise turning Masema's world upside down and inside out. The only way through it was to pivot his brain, and he started spinning like a top. Notice how he's nice and calm in Fal Dara, and ever since he's had more excuses than a farmboy caught in the hayloft?

Yes, we first see signs of his insanity in the scene at the end of tGH directly after Falme when the Shienarans swear fealty to Rand.