Entirely pet theories that may be untrue but worth considering:

- Nicotine helps mitigate the negative symptoms of ADHD, but US society has seen a major drop in tobacco usage

- Having access to a secretary greatly compensates for workplace related tasks that are difficult for those with ADHD. I have had a few conversations with people at my company much older than myself about how the number of secretaries has vastly shrunk. My boss’ secretary used to reach out to me about a meeting she had scheduled for us. Now my boss doesn’t have a secretary, and I have to schedule those meetings, update them, and communicate this with multiple parties while also having a full plate of my own dev work.

Not all of these are mutually exclusive, but there is also a fourth option:

- ADHD was severely underdiagnosed in the past and got more accurately diagnosed in recent years

If I'm reading the parent comment correctly, I think they're saying that that the high rates currently being diagnosed require one of their three conditions to be true.

That is, if ADHD is accurately diagnosed, and never had an evolutionary advantage, and isn't caused by some modern factor, then why would ADHD be so highly diagnosed today? Which is an interesting thought in my view

It could share a root cause with something that was evolutionarily adaptive or simply not have been sufficiently maladaptive to be strongly selected against.

There are other conditions. There's at least a cultural component in that we haven't always embraced mental health care in the US as much as we do today. Many other parts of the world still don't.

Whether over or underdiagnosed now, it was underdiagnosed in the past.