http://www.allaboutcounseling.com/codependency.htm

Why do we become codependent? What causes it?

It's widely believed we become codependent through living in systems (families) with rules that hinder development to some degree. The system (usually parents and relatives) has been developed in response to some problem such as alcoholism, mental illness or some other secret or problem.

General rules set-up within families that may cause codependency may include:

It's not okay to talk about problems

Feelings should not be expressed openly; keep feelings to yourself

Communication is best if indirect; one person acts as messenger between two others; known in therapy as triangulation

Be strong, good, right, perfect

Make us proud beyond realistic expectations

Don't be selfish

Do as I say not as I do

It's not okay to play or be playful

Don't rock the boat.

Many families have one or more of these rules in place within the family. These kinds of rules can constrict and strain the free and healthy development of people's self-esteem, and coping. As a result, children can develop non-helpful behavior characteristics, problems solving techniques, and reactions to situations in adult life