Clinical psychologist here - administered over 2000 IQ tests.

So let's see:

1. karpinski acknowledges this is only a preliminary study, no random sampling, no control groups.

2. She also notes there's no necessary causal relationship. There appears to be a correlation (high IQ individuals generally earn higher incomes and are much more likely to be diagnosed, therefore the actual fact could be a significantly larger number of low IQ individuals have depression or anxiety-related disorders but we don't know because they're not diagnosed.

3. You quoted her in just one sentence saying the overall IQ is highly misleading, because of the many smaller "subtests" of the overall IQ test, low scores on just 1 or 2 (particularly working memory, but processing speed is important too) can lower the overall IQ, which is why very often testers do not focus on the main IQ scores but look at "index scores" (for verbal, non-verbal/performance, working memory and processing speed).

4. I saw a reference to Genome wide association studies, which may suggest to the reader something about heritability. Despite all the advances in our understanding of genetics and heritability, the only reliable studies of heritability of psychological characteristics are "twins raised apart" studies. And for everything but schizophrenia, all of the existing studies have grave defects (for schizophrenia, major defects!)

So basically, this is an interesting suggestion with, so far, very little solid scientific research underlying it.

Finally, nobody even remotely agrees on what intelligence is, and the ignorance of this leads to unfortunate disparaging of IQ tests.

I not only explained this to all patients I tested, but included a paragraph or two on this in all my reports: IQ does NOT, as far as we understand it now, measure some abstract "intelligence." It's incredibly useful in certain limited spheres - for example as part of a large battery of tests, it does remarkably well in providing details to neurologists regarding the functioning of certain areas of the brain.

If it is applied with great care and precision in very limited areas, it can be helpful. Beyond that it is the subject of enormous abuse and confusion.