ADHD

Diagnosis is a relative thing. What do you mean, should you get diagnosed? Are you sure that ADHD isn't mentioned in your psychiatrist's chart? It might be hard for them to justify prescribing controlled substances in case of an audit if it's not. Right now most pharmacies and insurance don't require a diagnosis code to be sent to justify prescriptions, but it is something that's starting to get traction as the industry modernizes, even if slowly. But the diagnosis may already be there and may or may not be in your chart. If it is, it likely will get out as insurance companies often require large amounts of information to be sent to them as they tend to just deny claims and say, "we need more information", so the doctors have no choice but to send entire charts. Also, a lot of the big medical records systems tend not to have good security as well as the intermediaries that transmit data to insurance companies. There was just a big hack last year that shut down a whole bunch of systems due to the consolidation of various systems recently. Anyway, the only way to keep your diagnosis private is to ensure that your doctor doesn't use electronic records and you don't use insurance. Otherwise, it's going to get leaked eventually, somewhere.

Now as to whether that information will be used to discriminate against you, that's another story. It might be if you intend to emigrate and you likely will be excluded from high security clearance work due to general mental health discrimination in those areas. But otherwise, an employer is unlikely to go looking for the info, at least for now. Usually jobs didn't require disclosing medical conditions unless they require high physical labor, security clearance, or some other very specialized work that is very sensitive, so YMMV.

And, if you're in the US at least, the full repeal of Obamacare/ACA has stalled as conservatives have realized how bad that would hurt them. So it's being picked apart piece by piece instead, and the preexisting conditions part is low on the priority list as it would be high on impact and thus very unpopular if done alone without hiding it in a larger repeal of the ACA.

Anyway, I had similar concerns and decided it was well worth the risk. I may want to emigrate some day, so I have been avoiding an Autism diagnosis, but that has no treatment options for adults anyway, unlike the ADHD. And I no longer have a job with security clearance, so no concerns there.

For reference, I've worked in medical billing and charting technology for a couple of decades and I'm currently a software architect for a major health insurance company in the US.