Psychiatric diagnoses are, in some cases, mere mental constructs. Maybe they are names for conditions that really exist, but maybe not.

In 1978, a common diagnosis given to people admitted to the hospital was "neurasthenia." Nowadays, no one who goes into an emergency room is diagnosed with neurasthenia. Maybe bipolar disorder is a real thing that people have. And maybe not. It's a category that doctors put people in. Do all the people diagnosed with BP have the same disorder? - just with varied features. I don't know. Maybe we are lumping together apples wnd bananas.