Mentats Addiction

 is a form of addiction which can occur in Fallout, Fallout 2, Fallout 3, Fallout: New Vegas and Fallout Tactics.

Fallout, Fallout 2, Fallout Tactics
"You feel groggy."

Using Mentats carries a 15% chance of becoming addicted. The addiction lasts for 1 week.

Fallout 3 and Fallout: New Vegas
Using Mentats carries a 5% chance of becoming addicted.