Thoughts on chemical imbalance?

Chemical imbalance - real?

I (31F) was diagnosed unspecified bipolar disorder with mixed features and ADHD. My last episode ended up with me hospitalizing myself.

Does anyone else ever doubt the chemical imbalance theory? Like, how is it that people with bipolar “have a chemical imbalance” and other humans don’t?

I have a friend who has a masters in neuroscience and keeps trying to convince me that we don’t really know what bipolar, ADHD and all other mental health issues are. We don’t know what defines it, but it’s moreso solely because of our thoughts and life scenario. That the idea of a chemical imbalance is made up.

This actually infuriates me. What are your thoughts?