Yes, once in a while, these studies or surveys turn up to show that people in liberal countries are the happiest.
Could be.
But here in the United States, people on that side of the political spectrum have by far the most diagnoses of depression and take the most SSRI's.
There is no real evidence that confirms this, if the correlation is the number of medications prescribed + political beliefs, many liberals have more money and better health care, which means increased access and availability.
The same number, or more, of Trump supporters who suffer from undiagnosed mental illness is just as likely.