Thing with adult diagnoses for these is that most adults have adapted and are managing fine. But, the adults I've seen that did end up getting a diagnosis were no longer managing fine. I theorize there's two factors, one is family life - where you can't do your own decompression or coping as much anymore because you are Needed. The other is mental and physical resilience, once you're past 30 this starts to decline so your mental energy levels etc aren't as strong anymore.
Most adult diagnoses I've seen around me are people in their mid-30s, which is the same rough age as people start having burnout after spending their 20s doing all the things and growing into more responsible roles.
But that said, thanks to the internet, people learn to recognise the symptoms and know that there is help when they need it. In theory anyway, I know in the US and UK adult mental health care is expensive and/or unavailable.
Burnout wise, I lasted a couple of decades longer but at times it sure was quite a hell.
I now suspect I would have had a better time had I opted for treatment. Perhaps not burned out in the first place.
My best time professionally was when I had a boss who was tolerant of my working style - disorganized, spread across multiple projects, no two consecutive days on the same project, happy to help other groups for the smell of novelty, sometimes rather too happy to do that, but able to solve technical problems deemed hard and engaging.
In the UK, currently, adult ADHD care is basically broken.
The NHS will accept you on waiting lists, if you're in one or two lucky regions, you have to wait a few weeks, otherwise you have to wait years. If you are in a very unlucky region, you can randomly get dropped from the waiting list, and effectively barred from ever getting back on it, because someone looked at the referral and diagnosed you as not having ADHD. Under the NHS you are not entitled to a second opinion (hence why you don't get to go back on the list).
So the NHS has this system called "Right to Choose" (RTC) where private care providers can register to offer services to NHS patients, charged to the NHS. You go to your GP and you say: "Hi, I noticed that if I go on the NHS waiting list for an ADHD diagnosis, it's uncertain if it will come before or after the heat death of the universe. Can you please refer me to this private provider of my choice instead?" And if your GP knows what RTC is, you get on the private provider's waiting list which is often between to 2w and 1y.
Cool, so that solves it right? Okay, but what happens once you're diagnosed? If you decide to go with the medication route (somehow it's either Meds or therapy but not both - what?), they give you a prescription. You take it to your local pharmacy to fulfil, and you fulfil it at the NHS prescription cost (currently just under £10 per prescription). You do this for a few months, trying different things until you find something that works for you. Now what?
Most providers will tell you to move to a "Shared Care Agreement". They contact your GP and say: "Hi, this person needs meds, they're stable on these meds, can you take over prescribing them." and for a while some GPs would be like: "Sure, that seems like the right thing to do in this situation."
Recently the advice has been for GPs to drop SCAs for ADHD medication. Why? I honestly have no complete picture. But the gist seems to be that it costs the GP practice time and money, that the NHS doesn't reimburse. IDFK. To me it sounds like people with ADHD are being used as a pawn in some idiotic game of chess between the regional NHS authorities and whatever higher-ups set the budgets for those regional NHS authorities. The current move is "People with ADHD get fucked+". I guess we're waiting for the reply from the higher ups. This is a conference chess game and who knows if the privately owned Royal Mail is going to actually deliver the letters in a timely fashion.
So now people who have been stable on medication for months to years are suddenly being told that they have 6 months to get an NHS diagnosis (which in most cases takes at least a year) or switch to a private provider that the practice likes (whose waiting list is now almost inevitably close to a year because everyone else is in the same shoes).
So now that you've successfully managed to deal with a bunch of bullshit, get a diagnosis, deal with the pains of titration etc, you are suddenly told you have 6 months before you'll undoubtedly become unproductive and struggle to hold your job.
And on the Nth day, the devil started creating Hell, and then stopped 5 minutes later because he realised that the UK already existed and would suffice.
Most adult diagnoses I've seen around me are people in their mid-30s, which is the same rough age as people start having burnout after spending their 20s doing all the things and growing into more responsible roles.
But that said, thanks to the internet, people learn to recognise the symptoms and know that there is help when they need it. In theory anyway, I know in the US and UK adult mental health care is expensive and/or unavailable.