Chem Resistant

Chem Resistant (Clean Living in Van Buren) is a Fallout, Fallout 2, Fallout Tactics and Van Buren trait, as well as a Fallout 3 and a Fallout: New Vegas perk.

Fallout 3, Fallout: New Vegas
Having the Chem Resistant perk means you’re 50% less likely to develop an addiction to chems, like psycho or jet.