Med-X Addiction

Med-X addiction is a form of addiction which can occur in Fallout 3 and Fallout: New Vegas.

Fallout 3 and Fallout: New Vegas
Med-X has a 10% chance of causing addiction. When addicted, the player character suffers a -1 penalty to Agility and Intelligence.

Fallout 4
Med-X has a 25% chance of causing addiction. When addicted, the player character suffers a -1 penalty to Agility and -10 to Damage Resistance