Codependent relationships are characterized by a dysfunctional relationship wherein there is an extreme dependence of a person on the another.
It causes serious pain and affects the majority of Americans, both in and out of relationships. They all have one thing in common: They’ve lost the connection to their core.
A codependent relationship is a dysfunctional relationship where one person supports or enables another person’s addiction, poor mental health, immaturity, irresponsibility or underachievement (Wikipedia).
This pattern of excessive emotional reliance on another person can be self-defeating and even self-destructive.
Davis, historically, the concept of co-dependence "comes directly out of Alcoholics Anonymous, part of a dawning realization that the problem was not solely the addict, but also the family and friends who constitute a network for the alcoholic." The concept of codependency overlaps with, but developed in the mainstream independently from, the older psychoanalytic concept of the passive dependent personality which is attaching oneself to a stronger personality.
"Dependency" is well-established in psychological literature. Whereas early on psychoanalytic theory emphasized the oral character and structural basis of dependency, social learning theory considered a tendency to be acquired by learning and experience, and ethological attachment theory posited that attachment or affectional bonding is the basis for dependency.