Addicted
Traditionally, addiction meant that a character needs some consumable (ex; drug, drink) to be used regularly or the character will suffer a penalty from withdrawal. So when a character used Psycho for example, and becomes addicted to it, he would suffer once the Psycho wears off.
Each addiction was temporarily alleviated by taking more of whatever caused the addiction, but otherwise reduced AP by 1 when ignored. The causes of addictions could be seen in the character's profile screen on the Karma tab.
However, you can no longer get addicted to drugs unless you have the Chem Reliant trait. Historically though, any character could become addicted even without the Chem Reliant Trait, and such addictions would last 1 hour.
NOTE: The Tragic Card Game can actually cause an in-game addiction.