There is no single cause of all emotional affairs, but there has been plenty of research that might shed some light on this question. Most of the time, underlying dissatisfaction prompts married people to seek emotional support outside of their partnership.
According to research conducted by psychologist and infidelity expert Shirley Glass, 48% of men cited emotional dissatisfaction as the primary reason they cheated, while only 34% of women who had affairs said they were either happy or very happy in their marriage.
That isn’t very specific, but psychologist Mark Borg has some deeper insight. According to him, “The epidemic of emotional affairs coincides with a tendency that we have noticed for people in long-term relationships to defend themselves psychologically. That is, ironically, protect themselves from anxiety-provoking aspects of love.”
So, if you want to prevent an emotional affair in your relationship, the best thing you can do is be vulnerable with your spouse and maybe even give up a little bit of control.