This isn't true for autism, ADHD, bipolar or schizophrenia since some biological mechanisms are understood (even if these labels aren't perfect), so what are you talking about and what do you base it on?
Just because some symptoms are alleviated by a medication does not mean that must be related to the underlying mechanism. Many times medications are altering symptoms far removed from the initial cause.
Under the "mechanism" section in wikipedia there are multiple theories discussed: https://en.m.wikipedia.org/wiki/Schizophrenia
Anyone can be diagnosed with ADHD these days. And for all intents and purposes the patient might have 9/10 symptoms. But do they really have ADHD or is it something else? We don’t even have the capacity to figure that out right now because our understanding is so limited.
I got adhd since a kid and i the test was the same. Only they asked the parents and not me. But i think i rly got it…
Its like the south park episode where kids got diagnosed because the bible bored them…
I had a bunch of assessment in early childhood but I didn't figure out what exactly my set of issues were until I got assessed by a very good neuropsych later in life. I really wish I knew about this stuff in late childhood, would've explained a lot more! It's also sad that there are not many good neuropsychs out there and it's hard to evaluate who is good for most people.
One thing for the other intelligent people out there, your intelligence can often mask that you are not performing to your full potential, because it compensates and makes you perform 'good enough'. Unfortunately our medical system is more orientated towards fixing the people who's lives are in a mess vs people who are just OK, so those who hobble along often don't get the help they need. Sometimes wish there was an equivalent of doctor that focuses on making people perform their best vs. good enough sometimes, kind of like a coach.
[0] "Anatomy of An Epidemic", Robert Whittaker
We don't diagnose diabetes with a list of symptoms because we have a lab test (where we have picked an arbitrary value, but that's another story). We have no lab test for add. That is frustrating, and I think that adhd is probably overdisgnosed, but I think most are doing the best they can.
But notably also not done the majority of time in practice. It is seldom done to the level of say verifying your flu strain, let alone other more expensive and/or invasive tests which do not serve the patient's medical needs.