Phobias is one of Fallout GURPS disadvantages. See: Fallout GURPS.
A phobia is a fear of a specific item, creature, or circumstance. Many fears are reasonable, but a phobia is an unreasonable, unreasoning, morbid fear. The more common an object or situation, the greater the point value of a fear of it. If you have a phobia, you may temporarily master it by making a successful Will roll . . . but the fear persists. Even if you master a phobia, you will be at -2 IQ and -2 DX while the cause of your fear is present, and you must roll again every ten minutes to see if the fear overcomes you. If you fail a Will roll to overcome a phobia, you will cringe, flee, panic or otherwise react in a manner that precludes sensible action.”— Steve Jackson Games GURPS sources
With the abandonment of GURPS, Phobias was removed from the game. Owing to the number of calls to it, there were three specific phobias in the game.