But if you look at the way they're defining social construct, these other conditions meet the same criteria they appear to be applying - can't be diagnosed by a brain scan and are based on clinical standards that are also very subjective. As is evidenced by the fact that they've changed significantly over the years and have been disputed, quite strenuously at times, and will probably continue to be changed and disputed. In other words, the criteria for these other diagnoses aren't unquestionably solid or objective either and that seems to be the basis on which the argument is being made, regardless of the fact that some people diagnosed with these conditions may be more easily identifiable to someone with a limited understanding of ADHD.
And nor are these other conditions necessarily more severe if you actually compare like for like - your post appears to take examples of severe schizophrenia and depression and then compare them with what are merely one or two of the milder traits associated with ADHD (that alone wouldn't come near to meeting the bar for diagnosis - even a "mild" one). I would suggest that you haven't really considered what having more extreme versions of these symptoms plus a few dozen others actually means for the people who live with them (or the fact that people tend not to share their biggest failures if it's avoidable but may be more likely to share the more insignificant every day frustrations).
ADHD has been linked, either directly or indirectly, to a higher likelihood of losing your job, experiencing marriage breakdown and all the distress and mental health issues that come with these things. To failing or underperforming academically and being condemned to vastly reduced life outcomes as a result. To being unable to maintain a romantic relationship or healthy friendships due to emotional volatility leading to social isolation. To succumbing to drug, alcohol and gambling addictions, to having your kids taken off you by social services because you cannot clean and tidy your house, keep your kids clean or consistently cook or prepare them food, and sometimes to impulsive, criminal behaviour resulting in jail, homelessness, road accidents etc as well as earlier death from all causes, including suicide. Many kids with ADHD are not safe when not on their meds as they are impulsive in a way that puts themselves and others in frequent danger.
It's not merely losing your keys a lot and paying your bills a few days late although these are the kinds of symptoms that people might moan about because it's what's happened that morning. All my friends know I'm always losing my keys. They have no idea about some of the other things that were a factor in getting my diagnosis.
You also didn't answer the main part of my question - can you think of any other examples of a social construct that responds positively and so significantly to medication in placebo controlled clinical trials?