Codein is habit-forming.

Codeine is an opioid pain medication. An opioid is sometimes called a narcotic.

Codeine is used to treat mild to moderately severe pain.

Codeine may also be used for purposes not listed in this medication guide.
Important information about codeine

Codeine may be habit-forming (IMHO it definitely IS) and should be used only by the person for whom it was prescribed. Never share codeine with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.

This info was taken from a website whose URL I unfortunately did´nt copy.