Yes they would. If you ask people if they're happy they'll say yes. If you actually measure it by observing what people do they'll exhibit behavior that shows they're not actually happy.

Self-delusion is a well researched topic. There are many studies.

> If you actually measure it by observing what people do they'll exhibit behavior that shows they're not actually happy.

The best part of this notion is the inverse where miserable people are doing happy people things.

> The best part of this notion is the inverse where miserable people are doing happy people thing

Sartre called it “bad faith”.

https://en.wikipedia.org/wiki/Bad_faith_(existentialism)

I know a lot of religious people like this. On the outside, they seem like the happiest people you’ve ever met, but once you get to know them, it turns out that they are miserable, and that the religious beliefs and behavior that they embrace are used to self-regulate their mental states. The more extreme religious people appear to be suffering a type of scrupulosity unique to disorders like OCD, and many sufferers will tell you that they are not happy.