The perk has two ranks, with the first one being similar to the one in Fallout 3 and Fallout: New Vegas, as it reduces the chance to become addicted by fifty percent. The second rank grants complete immunity to addictions. In Fallout 4, the perk is an early to mid game perk, whereas Fallout 76 treats it as a late game perk.
The perk functions differently than for all the other games, instead of reducing the chance to become addicted it allows the player character to take damage to hit points, when otherwise they would become addicted to a drug. It is also possible to discard the perk to remove an "Addicted" trait.