Theism and Supernaturalism are ideas that God, gods, spirits etc exist.
Theism and happiness
Some types of theism mean that people believe in gods or spirits who help us and give wonderful things in an imaginary afterlife. Such types of theism can genuinely make people happy. Some types of New Age beliefs are that type as is Christian Universalism. Rational people think such people are happy with illusions.
Theism and unhappiness
Other types of theism and supernaturalism get believers terrified of ghosts, devils, other malevolent spirits etc. Believers in that type of superstition are quite likely less happy than they would be as atheists.
Christian fundamentalists tend to preach Hellfire and teach followers to fear a malevolent, angry god. They typically are so frightened that they can’t let themselves see that their imaginary god does not love. God-fearing Christians can’t easily examine other rational reasons for doubt either. God-fearing Christians are quite likely less happy than they would be as atheists but they fear god so much they can’t even admit to themselves that they are unhappy. Hellfire type Christians all too often evangelize and try to get happy people to be miserable with them.