So a couple points here. Probably at least 50% of family history of "bipolar disorder" is garbage, if you're at all aware of what the community standards for a "bipolar" diagnosis have typically been. We're starting to approach that with ADHD these days but I digress....
Putting that totally aside, yes you should be screening for bipolar disorder in the same way you should be screening for any other psychiatric comorbidity. Because if, of course, one was familiar with DSM criteria, they would be paying attention to the last part of ADHD criteria:
"The symptoms do not occur exclusively during the course of schizophrenia or anotherpsychotic disorder and are not better explained by another mental disorder (e.g., mood disorder, anxiety disorder, dissociative disorder, personality disorder, substance intoxication or withdrawal)."
I'm just gonna be frank and say bipolar disorder (as it is classically defined) and ADHD are not difficult things to distinguish from each other for anyone who's putting in even the minimal amount of diagnostic effort. It's making a problem where really one shouldn't exist. They should, as currently defined, have completely different developmental trajectories and clinical presentations. At the most basic level, there should be no episodic nature to ADHD symptoms. In my experience, even when I'm semi-suspicious of mania and kids screen positive on the CMRS or ASRM parent or child rating screeners, when I go more in depth on the symptoms, they either seem to be normal range or not bipolar disorder (vast majority of the time they're screening positive for crappy sleep chronically, "talking more than usual" chronically or chronic hyperactivity).
The issue of course from Ghaemi's end is that in the expansionist camp of manic/depressive illness, many more symptoms COULD be bipolar disorder or COULD go on to be bipolar disorder in the future. I mean just read the article, read most of what he writes in general. He says that "none of the definitions" of any other diagnosis are meaningful and it's doesn't really matter if you don't diagnose them with bipolar disorder right away, as long as you don't diagnose any other of those lame not real diagnoses and don't give them any of those bad meds.
We can pull examples all day of odd or again, disingenuous statistics or interpretations of studies.
"About 90% of all children who meet mania criteria also meet ADHD criteria, because distractibility is one of the core criteria for mania."
What? By who? A criteria of ADHD is that symptoms must persist for at least 6 months. Is he saying all these kids were hypomanic or manic for 6 months straight?
Who's making the strawman argument here? This quote comes right after an entire article where he literally craps on clinicians who diagnose kids with a family history of bipolar disorder with other conditions (I have the sneaking suspicion that maybe because he doesn't actually understand heritability vs recurrence risk). I quote again:
"
It is completely illogical, for instance, to claim that a child had “major depressive disorder” (MDD) or
ADHD when there are immediate family members with bipolar disorder."