Paranoia

From Srafopedia

Paranoia is a disturbed thought process characterized by excessive anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs concerning a perceived threat.

In The Subtle Knife, Will's mother, Elaine, is described as behaving in an apparently paranoid manner, although we later learn that the threats to her and Will were real, rather than simply perceived.