I would say yes. My son does. Some days he is more up and down than others. Sometimes it is due to weather, his sleep, or what he has eaten that day 🤷‍♀️

I've always had behavior problems they use to be a lot of meltdowns not so many know. My wife has adjusted to them.

yes very common

Yes it is possible. I can speak in my behalf. I am bipolar.

Absolutely. My son has a splintered profile. His sensory needs change like the weather, so things can go up and down quite randomly