"Codependency" is a term used to describe a relationship in which, by being caring, highly functional, and helpful, one person is said to support, perpetuate, or “enable” a loved one’s irresponsible or destructive behavior. For example, helping an inebriated spouse navigate an embarrassing situation or providing living quarters for a substance-using young-adult child is said to be counterproductive, a way of forestalling recovery and actually perpetuating the problem.
According to this way of thinking, creating emotional distance from the troubled loved one is necessary and beneficial to that person: It is a way to expose them to the negative consequences of their behavior.
In being reliable, caring, and nurturing, the co-dependent partner is perceived to be exhibiting any number of weaknesses of his or her own—from low self-esteem and an excessive need to please others to poor interpersonal boundaries that make him or her feel responsible for the other’s problems.
This controversial concept emerged in the substance-abuse community in the 1980s and was originally applied to caretaking patterns seen among partners of alcoholics. It has since been applied not only to addictions in general but well beyond, to other kinds of mental health and behavioral problems, including domestic violence and emotional abuse.
The term is also often used colloquially, to describe close relationships without carrying any strict psychological meaning.