In case anyone is interested in an attempt at an answer ...

An important evolutionary benefit of a large brain is that it can run simulations of future events. These simulations use the same brain structures that respond to actual events, but with the physical actions suppressed. Thus I imagine going down the hill to the shop and getting caught in the rain with no coat. I imagine feeling cold and wet on the way home and avoid the actuality by taking a coat.

I avoid the actual at the price of suffering the imaginary. The smarter one is, the sharper, and more painful, and more active one's imagination.

Everyone was getting old fast, and they were leaving this Earth for good. — Corvus

Poor old Corvus not only has to get old and die eventually, as we all do, he has to imagine getting old and dying over and over again even while he is actually young and in his prime. So even the good times are bad.

Poor old Corvus not only has to get old and die eventually, as we all do, he has to imagine getting old and dying over and over again even while he is actually young and in his prime. So even the good times are bad. — unenlightened

Like many, I don't keep thinking about my own ageing and death. But it is the news of the others who have been dying, seem the cause for unhappiness I guess. But is happiness always best thing in life?
Some say happiness is self deception and illusion caused by ignorance.

In the case of the pre Aristotle thinkers, knowledge and wisdom seem to have been pursued with more avidity than happiness.

To me, happiness without wisdom and understanding is meaningless. Essentially blissful ignorance. Ideally one gets rid of the ignorant part and maintains the bliss.

However, the road from ignorance to understanding is a perilous one. With the realization that one's prior understanding of one's existence is insufficient, the bliss is the first to go and will only remain there as a distant promise.

Many people strand along the way. Intellectively capable enough to no longer remain ignorant, but lacking the fortitude of mind and soul to reach a form of wisdom and understanding.

Yeah, but what's the value of "happiness"? (Well-stocked) drunks & heroine junkies, or the lobotomized, are quite "happy" moment to moment. Smart & stupid, it seems, are complementary rather than mutually exclusive capabilities: the latter being the maladaptive mis/ab-use of the former (which consists in the adequate match-up of means with ends and/or expectations with circumstances). Many smart-idiots are miserable; also, many are content or even happy. Speaking for myself, I'm happier striving for the disposition, or mental state, of 'sad Socrates' instead of 'satisified swine'.

But is happiness always best thing in life? — Corvus

I prefer happiness to unhappiness, but for plastering a wall, I would go for a plasterer's trowel. That seems to me to be how the the word works. It's akin to asking what's better than good. I have already suggested the evolutionary benefit of intelligence which depends to a great extent on the environment, but as to pursuit of knowledge and wisdom, well I do it (at a leisurely pace) because it makes me happy, or at least happier than pursuit of ignorance and folly.

Smart & stupid, it seems, are complementary rather than mutually exclusive capabilities: — 180 Proof

Well, you can go to your college, you can go to your school
But if you ain't got Jesus, you's an educated fool
And that's all, I'll tell you that's all
'Cause you better have Jesus
I tell you that's all. — Ry Cooder

Cause they don't think too much.

I prefer happiness to unhappiness, but for plastering a wall, I would go for a plasterer's trowel. That seems to me to be how the the word works. It's akin to asking what's better than good. I have already suggested the evolutionary benefit of intelligence which depends to a great extent on the environment, but as to pursuit of knowledge and wisdom, well I do it (at a leisurely pace) because it makes me happy, or at least happier than pursuit of ignorance and folly. — unenlightened

If you know how to make yourself happy, then that is a great knowhow. The Good thing about happiness acquired via knowledge and wisdom lasts, unlike happiness derived from ignorance or illusion, which is usually short-lived.

The problem with this thread is that the articles you posted don't conclude that intelligence and happiness are inversely related. Point out specifically what you're saying those articles say that supports your thesis that intelligent people are unhappier than dumb people. I read them to say that intelligence and happiness are not correlated, whether that intelligence be high or low.