Psycho Addiction

Psycho addiction is a form of addiction which can occur in Fallout, Fallout 2, 'Fallout Tactics, Fallout 3, Fallout: New Vegas, Fallout 4, and Fallout 76''.

Fallout, Fallout 2, Fallout Tactics
Psycho has a 20% chance to cause an addiction. It lasts for a week. When addicted, the player character suffers a 2 point penalty to Intelligence.

In Fallout Tactics, the penalty is very different: Damage Resistance is reduced by 25 and Agility by 3, while Intelligence is actually increased by 1.

Fallout 3
Psycho has a 10% chance to cause an addiction. When addicted, the player character suffers a 1 point penalty to Endurance and Perception.