> Self diagnosis is not reliable

Professional diagnosis is not reliable either. ADHD and autism are often misdiagnosed as one-another, especially in girls.

> If you don't have an official diagnosis you can't be certain you really have ADHD

A lot of the time, the mental health professional making the determination doesn't have specialty in ADHD/Autism. All they're doing is looking at symptoms and making their best guess. Which is exactly what people are doing when they make a self-determination. In many cases, people with high-functioning autism know more about autism than the people who are supposed to know. And it's not like the diagnoses can be validated when we're still figuring out what autism even is.