I interviewed three experts in the psychiatric field to find out. Here is what they had to say:
Where does jealousy come from?
Jealousy usually comes from feelings of insecurity. We don't feel good about ourselves, so we worry that other people have the same low opinion of us. Sometimes this comes from past experiences, like being told that you weren't worthy. -- Vanessa Marin, sex therapist
Jealousy is predicated on a lack of trust. Why isn't there trust? You may not have had solid relationships in the past. Maybe you were even cheated on before. -- Henry B. Hartman, PhD, clinical psychologist
I think jealousy has its roots in the fact that some people know that they themselves cannot be trusted. In this case, the jealousy does not stem from the actions of a significant other but from their own current desires or past actions. They would cheat, therefore everyone would cheat. And if everyone cheats, then they must make sure those they love do not cheat. They become jealous and controlling. -- Diane Urban, PhD, licensed NYS psychologist, college professor