K.B.
Yes a child as young as 2 can exhibit bipolar or mood disorder, especially if they are "gifted" or advanced for their age.
Advanced children can show "behavior problems", they question authority figures more, they may seem hyper, or just in their own world.
My son is six years old, he has always had aggression issues, and "tested" authority figures. It was frustrating to say the least. He is a very lovable child and would show empathy. But at times he will show a lot of aggressive behavior. He has been tested as gifted. He is showing signs of possible ADHD, as he says I feel like a spring inside, and I try so hard to calm down, but I just can't.
I wish I would have pushed for theraphy sooner. I kept thinking it was something that I would help him through. I was being told it was a phase, and try this or try that.
He has gotten better since he can communicate his feelings better. I knew he needed some help when he was able to tell me he wants help with how he feels inside ( it was heart breaking). He goes for his first evaluation next week.
I know somethings that has helped us was rountine and letting him know his schedule and be apart of making his schedule. Free play with little or no say from me, of course you have to keep them safe, his favorite thing is hiking in the woods, breaking open nuts or sticks and discoving things.
I think you are exactly in the right direction, about seeking further help.
Best of luck!