You used the drug Ultrajet once too often and now your body is craving for more... and more... and more... well done! You got yourself addicted.
Ultrajet addiction is a form of addiction which can occur in Fallout 3 and Fallout: New Vegas. Ultrajet addiction is permanent, meaning it cannot be cured by doctors or Fixer.
A 20% chance of Addiction, resulting in a -2 penalty to Agility and Strength as well as -1 to Perception.