I actually would not expect smart people to be happier. In fact, I wouldn't expect any group of people to be particularly happier than anyone else.
Happiness and suffering are two sides of the same coin and we evolved these feelings (or they were bestowed upon us by God, either way) in order to guide us. We do more of what feels good, less of what feels bad.
If we're happy all the time, happiness loses its intended purpose. Same for suffering.
That's why, no matter what financial windfall you may experience, give it 6 months and you'll be just as miserable (or worse) as you were before. But because you got a high off of it initially, you keep pursuing more and more, always convinced the next upgrade in your life is what will do the trick. But it doesn't. All you're doing is raising the bar for what it takes to make you momentarily happy.
It's the "poverty of affluence", as described by Paul Wachtel in his book by the same name.
So our minds are constantly adapting to our circumstances and rebalancing things so that we come back to the center.
Chasing happiness, much like running away from suffering, is a fool's game. We are hard wired to feel both in roughly equal measure, regardless of our circumstances, over the long haul.
For this reason, I think the buddhists and stoics have it right. The best thing we can do is nothing. Sit down and shut up. Get off the wheel of suffering, observe the world as dispassionately as possible, and accept both joy and suffering as inconsequential inputs meant to guide us.
It's the closest any human will ever be allowed to experience peace in their mortal life. If you chase the highs of life, expect massive lows, as well. Accept life on life's terms. Stop chasing things and you may not be happier, but you'll probably be less miserable and experience fewer bouts of crippling depression and anxiety.
Or as Charles Bukowski's epitaph famously reads: Don't try.