Well, I wish I could say that Dagmar had "early symptoms" but there was nothing. She didn't cry more than any other baby and was always a good sleeper-so although the link is intriguing, and may help predict future problems, I guess it isn't an absolute indicator.
Boys also tend to be worse sleepers than girls in my experience. Granted, that experience is based solely on anecdotal evidence since it seems I will never have a son of my own.
But everyone I know who's had both says that the boys were definitely worse-worse sleepers, cried more, wanted to be fed more, etc. So don't get worried just yet, ukladybug. There's plenty of time for you to freak out about his mental state, physical state, ability to live a normal life, ability to make friends/throw a ball/spell/read/drive/play ball/do math/get into college/not be a serial killer. It's all ahead of you-what a joy!