I'd place a pretty big wager on it, and I'm not usually much of a gambler. Of course, what they have to do with each other is a completely different question. Are the ghost Pokemon causing the nightmares? Were they attracted by the same force that's been causing them, if they aren't the ones doing it? Were they sent to hinder us from helping the ones who are sleeping? I think if we could answer that question, we'd be a lot closer to finding the source of all this.