Which is a defining symptom of derealization?

The defining symptom of derealization is characterized by experiences of unreality regarding one's surroundings. This disorder is marked by a sense of detachment from the environment, where individuals may perceive their surroundings as dreamlike, surreal, or distorted. They might feel as though they are living in a movie or that the world around them lacks genuine substance or emotion. This sense of altered perception can lead to significant distress and impact daily functioning.

In contrast, while delusions of grandeur involve an inflated sense of self-importance, feeling detached from one's thoughts pertains to depersonalization rather than derealization. Severe anxiety attacks may accompany various anxiety disorders but are not specific to derealization. Therefore, the most accurate representation of a defining symptom for derealization is the experiences of unreality regarding one's environment.