Emotional abuse can be worse than physical abuse.

It is not against the law for an adult to say mean things to another adult. It is not against the law for an adult to play head games with another adult. So, no, emotional abuse usually can not be prosecuted.

If you are an adult and another adult is being mean to you, then you have the responsibility to terminate your relationship with your abuser. The law does offer some protection to adults who can not terminate a relationship, for instance when your abuser is someone you work with. There are laws against creating a hostile work environment. Children can be removed from the custody of emotionally abusive parents. But, no, there is no law that says people whom you chose to be associate with have to be nice to you. The government can't protect us from making unwise choices about the relationships we enter into.