Bipolar Disorder is not usually diagnosed in children under 6 and even then many doctors are not sure of the child having Bipolar when it could be ADHD (Attention Deficit Hyperactive Disorder). If your child is diagnosed with Bipolar Disorder you might want to get a second opinion with a doctor you trust.
Now I had Bipolar as a child. I would have been around 6 years old although my anxiety started as an infant. I am 59 now and back then they didn’t discuss mental health concerns.
I went through my teens not understanding what was happening to me. The mood swings. The mania where I didn’t sleep for 3 months and then the depression. I had rage issues although they were usually kept inside. I did more banging of things than breaking things like my son whose rage had him breaking things all the time. It has just been lately that I started to act on my rage issues outwardly.
I tended to isolate as a teen and stay in my room and read. My parents would insist I go out and play with the rest of the kids and my siblings. I didn’t want to. I still isolate, but nobody can make me go outside anymore. I am old enough to make that decision on my own although everyone is always trying to talk me into going out. I do sometimes, but if I don’t have to I don’t. I would be a hermit is people would just leave me alone.