Med-X Addiction

Med-X addiction is a form of addiction which can occur in Fallout 3, Fallout: New Vegas, Fallout 4, and Fallout 76 after consuming Med-X.

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

In the Fallout: New Vegas quest Bye Bye Love, a Medicine check allows the player to tell Joana that her 'contracted pupils and involuntary spasms' are signs of Med-X addiction.

Fallout 4
Med-X has a 25% chance of causing an addiction. When addicted, the player character suffers a 1 point penalty to Agility and 10 point penalty to Damage Resistance. The addiction can be cured by visiting a doctor, taking Addictol, eating a radscorpion egg omelette or drinking a refreshing beverage.