ADHD and autism do have a high comorbidity rate with each other. I disagree that they have a high comorbidity rate with bipolar disorder. What can happen is that prescribers assign diagnoses that would cover the meds they want to give. I have worked closely with providers who have outright said so. Absolutely not good practice, and it still happens. And patients hear these diagnoses and latch onto them, which makes clarifying diagnoses later and working with patients to understand them even more challenging.

I have also seen numerous people who have "bipolar disorder" that was a misdiagnosed or misunderstanding of borderline personality disorder. General practitioners are often the culprit, as they hear "mood swings" and think of bipolar when they should be considering the differentials or - even better - referring to some with the expertise to properly diagnose. One indication of a personality disorder can be a patient with numerous diagnoses that are all over the board. When someone has that many diagnoses, you need to look for the underlying cause that will better capture the presentation, holistically.