It's an inkjet thing.
When you run out of color, Brother lets you select to print using only black ink. But after 4 weeks, they lock you out from that too.
It's documented on their website. No more printing at that point until you replace the offending color cartridge. They do at least let you scan though.
Meanwhile I have printed exactly one single black-only page since the last time I put in a new yellow cartridge (3 months ago) and yet my yellow ink is almost 1/4 depleted at this point. I've just been watching it slowly disappear.
The scientific, peer-reviewed answer is that it is significantly under-diagnosed in adults as well as in those AFAB of all ages. Most sources say up to 80% of adults with ADHD are undiagnosed and/or untreated.