Are highly intelligent people more likely to be unhappy, and why?

I read this quote that intelligence and happiness as a combination is rare, something along those lines.

I feel a lot of very smart people are very serious and so it makes me wonder if there's a correlation between the two.

If that is the case, then why do so many people aspire to be lawyers, bankers etc. It can't be just for the money as there's just as much money in other things for example nowadays trades is making insane amounts.

Are highly intelligent people more likely to be unhappy, and why?
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