There is good evidence to show that religion and happiness go together. In an article in Psychology Today a few years ago, Clay Routledge said, “Are religious people happier than non-religious people? The short answer is yes.” Some may find that surprising, but the evidence is clear.
It seems that not all religions are equally linked with happiness. Catholic and Protestant Christians tend to be happy, as do Buddhists. However, Eastern Orthodox Christians were found to be the least happy. Jews, Hindus, Muslims, and the non-religious were in between.
In fact, ‘religions’ differ from each other in so many ways that it is rather misleading to lump them all together under the same heading. One important difference is that some religions are very much matters of cultural and racial identity. That is true of Jews, Hindus and Muslims. It would be an odd question to ask a Jew what his ‘religion’ was; he/she simply is a Jew.
Christianity is much less like that. It is a religion that you opt in to, or opt out of. Buddhism, at least in the West, is also that kind of religion. This may partly explain why they have a different relationship with happiness. It is also important to bear in mind that the evidence doesn’t show that religion actually makes people happier; it could be equally well be that happy people choose to be religious.
Religions also differ in how much they encourage personal spirituality, as well as attendance at public religious observances. My guess is that private spirituality (prayer, etc.) tends to be good for happiness, more than public religious observances. I suspect that Christianity and Buddhism encourage private spirituality more than other religions. If so, that may be another reason why they are more closely linked with happiness.
The puzzle in the data from this study is why Eastern Orthodox Christians (Russians, Greeks etc.) have the lowest happiness and life satisfaction rates of all. They have the same basic Christian beliefs as Catholics and Protestants, so that can’t be the key thing.
Following up on my previous suggestions, it may be that they are more matters of cultural identity than other forms of Christianity, and they may encourage personal spirituality less. But it will take more research to drill down into why, unlike any other religion, they are associated with unhappiness.