This claim needs citation.
The overall point is that the cost of the false positive overweighs the cost of the false negative
I would say the point of the article is here is a list of reasons why it might be over-diagnosed, some people on both sides of that, 50% puffed up with human interest pap about the Boy Whisperer
It's bad for kids to be on pills.
One of the most important questions you can ask your doctor is "what happens if we just do watchful waiting?"
Taking meds, with their potential risk, if they provide no benefit is a bad thing.
While ADHD is real and needs treatment some of the people being medicated either have other diagnoses or they have bad parents. This isn't something that should be passed onto the child ("there is something wrong with you, take these meds") when it is the family that is broken ("I need to learn some better parenting techniques; we need to set firmer boundaries").
Is 13% to 27% sufficiently co-morbid for you?
That is just one of the first results for "adhd depression". I've seen studies with cited numbers far higher than that for people who are untreated.