The biggest way to know if it's Asperger's-related is WHY he has the mood swings. Are the outbursts related to sensory issues? Change? Disruption in routine? Is the giddiness related to talking about an obsessive fixation/"special interest?" Do the mood swings stop relatively quickly, such as when a bright light is taken away or when an annoying sound is stopped? If so, then this is Asperger's. If he has signs of Asperger's, and if the mood swings get worse when the Asperger's symptoms do, I'd say that this is because the mood swings are a cause of the Asperger's. Bipolar disorder in children is very, very rare. Also, bipolar moods are pervasive and last throughout many situations. A bipolar patient can't "switch off" their moods. So, if a bipolar Aspie was depressed, having him engage in talking about his special interest wouldn't make him any less depressed. But if he's having an Aspie mood swing, where he's having an outburst or anxiety, having him talk about the obsession will help calm him and make him happy, perhaps even switch into "giddy mode." You should ask your doctor to just keep an eye on your son's mood swings, but it sounds like typical Aspie mood swings to me. I'm on a mood stabilizer for mine. Several doctors (and myself) thought I had cyclothymia, a very mild form of bipolar disorder. That's how up-and-down I'd be. However, it was all from sensory issues, change/disruption in routine, and obsessions. Sometimes, you really have to look hard for the trigger because it can be very slight. Even the Aspie doesn't know why they get upset. We often don't know until afterwards. Good luck, God bless, and if you have any questions, feel free to ask!