Codependency is a type of dysfunctional helping relationship where one person supports or enables another person's drug addiction, alcoholism, gambling addiction, poor mental health, immaturity, irresponsibility, or under-achievement. Among the core characteristics of codependency, the most common theme is an excessive reliance on other people for approval and a sense of identity. Given its grassroots origin, the precise definition of codependency varies based on the source but can be generally characterized as a subclinical and situational or episodic behavior similar to that of dependent personality disorder. In its broadest definition, a codependent is someone who cannot function from their innate self and whose thinking and behavior is instead organized around another person, or even a process, or substance. In this context, people who are addicted to a substance, like drugs, or a process, like gambling or sex, can also be considered codependent. In its most narrow definition, it requires one person to be physically or psychologically addicted, such as to heroin, and the second person to be psychologically dependent on that behavior. Some users of the codependency concept use the word as an alternative to using the concept of dysfunctional families, without statements that classify it as a disease.
According to disability studies specialist Lennard J. 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." "While not an actual diagnosis, the term “codependent” was first used to describe how family members of individuals with substance abuse issues might actually interfere with recovery by overhelping." It was subsequently broadened to cover the way "that the codependent person is fixated on another person for approval, sustenance, and so on." 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. All three theories have contributed to the concept of dependent personality disorder as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association. The definition and criteria have changed in the different versions of the DSM. In DSM-I, passive dependency personality was characterized by helplessness, denial, and indecisiveness, and was considered a subtype of passive aggressive personality. By DSM-IV, there were nine criteria with an essential feature of a pervasive or lifetime pattern of dependent and submissive behavior. The DSM-IV definition emphasized the excessive need to be taken care of, leading to submissive and clinging behavior and fear of separation.