4 is too young to be bipolar or anything else. Mental illness shouldn't be diagnosed in anybody under 8 years old. That's what's wrong in this country. Your child has tantrums and you give him Lithium. I know this. I've been misdiagnosed bipolar and lithium nearly killed my brain. I am against this bipolar over diagnosis. My dad is bipolar, but his started at 21. In children you can't tell. I may not be schizophrenic, although it sure looks like it.