A recent paper looks at how the disorder correlates with future earnings:
The employment reduction is between 10 and 14 percentage points, the earnings reduction is approximately 33%, and the increase in social assistance is 15 points, figures that are larger than many estimates of the Black people/White people earnings gap and the gender earnings gap.
Austin Frakt analyzes:
Needless to say, these are huge effects. It makes me wonder whether, to the extent it is over-diagnosed, ADHD is serving as a proxy for characteristics predictive of poor labor market outcomes. That is, Johnny is looking like he’s not succeeding in school (itself suggesting reduced earnings and employment potential), but maybe an ADHD diagnosis and the associated meds will help him. But maybe they actually don’t help much. Alternatively, maybe there is a self-fulfilling stigma to the diagnosis. Of course the straight-forward interpretation that ADHD is legitimately bad for your future is perfectly fine.