Again, good question. Berean makes a good point: is the "happy" proportion among JW's approximately the same in other religions? I dunno.
I do, however, know a couple of extremely happy, well-adjusted Witness families. They would, in fact, still associate with my inactive self if I encouraged it. They are genuinely nice people, their kids turned out good, their marriages are solid.
I have taken the somewhat unpopular position that not everyone who was raised in or exposed to the cult of JW's (and make no mistake, it IS a cult) becomes permanently, irreversibly damaged. Perhaps the majority are, but I don't think there are any conclusive studies. If I can site two or three examples of blissfully happy JW's, there must be more. I'm not talking about the artificial "happiness" you see in the DC dramas - I'm talking about how people are in every day life.
One family in particular I lived with for a period of two months when our home was being built. I saw them each and every day, and believe me...that's too long to "fake it". They had an enviable marriage, loving appreciative kids, and a great attitude towards outsiders. Sounds rare, I know, but it was the real deal.
Me? I had my happy moments. When I was ignorant of the erroneous doctrines, I was probably happy. Once the scales fell from my eyes, I got and stayed unhappy until I left. I had one of those happy endings, though.
(Roll credits)