Fallout 3 addictions

Overview
Unlike previous titles, addiction is permanent in Fallout 3. Each chem carries its own risk of addiction, as well as primary statistic debuffs once addicted. Chems also have what is called a "usage monitor effect," or "UMON," which is a value that accumulates with successive hits of the particular chem, raising the chance of addiction after each hit. A UMON value of 75 equates to an additional 1% chance of addiction, while a value of 175 equates to a 100% chance of becoming addicted.

Addictions can, however, be cured for a price by visiting a doctor. If the player character owns a house in either Megaton or Tenpenny Tower, the addiction can be cleared for free if the player character also owns a My First Laboratory house improvement. The healing archways in Mothership Zeta remove also addictions among their other healing effects.

Legend
1This only applies to plain Mentats; the other variations (Berry Mentats, Orange Mentats, and Grape Mentats) are non addictive.
 * Risk is a base chance of addiction per use for alcohol only.
 * UMON is an accumulating chance of addiction for chems. See above for a detailed explanation.
 * Duration is the length of time required to pass without consuming the drug for the accumulated UMON value to be reduced.