Co-dependency is a term from psychiatry. In certain cases, people knowing an addict can increase the addiction through their actions. As an example, take a person who is an alcoholic. Because of alcoholism, that person is not as productive as his colleagues at work. Colleagues at work may work more and compensate for the work the alcoholic has not done. A similar case can be made for family members who help finance a dependency.

Someone suffering from codependency will not be able to self-soothe and will rely on their partner in order to meet their own emotional needs. Codependence can cause an irrational fear of rejection and being alone. Codependence can be one-sided, or both partners may suffer from it.

In a codependent relationship, individuals put the other person’s needs before their own, often sacrificing their own integrity and sense of self in the process. Codependency can cause a person to have an overinflated belief that they alone are responsible for affecting the beliefs, thoughts, emotions, and behaviours of those around them.

Causes of Codependency 

 Codependency is often thought to be a result of living with alcoholic parents or other family members who struggle with substance abuse.
 Codependency may begin in childhood, as children often grow up modeling behaviors after a parent who may have been codependent or in a codependent relationship.
 Codependency may also be the result of a traumatic event, whether in childhood or adulthood.
 A complex relationship between codependency and narcissism has been established, indicating that the two often go hand in hand, and even sometimes overlap.

While childhood abuse, traumatic experiences, and exposure to narcissistic behaviors of parents and/or partners seem to play a role, it is difficult to predict codependency on the basis of any of these factors alone.

Symptoms of Codependency 
There are two main forms of codependence: passive and active.  Someone who is passively codependent is more likely to avoid conflict and confrontation, going to great lengths to keep things smooth and not rock the boat. Active codependency is often more manipulative, and an individual may try to push their partner into behaving a certain way in order to fill their own emotional needs. 

Both forms of codependence have many things in common, however. Some common signs of codependency include:

 Putting the feelings of others above oneself: Someone who suffers from codependence will often sacrifice their own feelings and wellbeing in order to make their partner happy.
 ''Constrained ability to assert oneself: With codependence, a person will rarely stand up for themselves, and if they do, it is often followed by intense bouts of guilt. 
 Fear of rejection, abandonment, and isolation: The fear of being alone can be so intense that many behaviors are molded around this. A person may go to extreme lengths to hold on to relationships.
 Trouble making decisions without others: A person may be so wrapped up in their partner’s needs and wants that they are unable to assert their own. 
 Need for control: Codependency breeds a strong need to control one’s environment and people around them.
 Efforts to be the one others depend on'': Codependency can cause a person to feel the overwhelming need to be the caretaker and thus become indispensable to those around them.

References

Psychiatry