Depersonalization is a dissociative phenomenon characterized by a subjective feeling of detachment from oneself, manifesting as a sense of disconnection from one's thoughts, emotions, sensations, or actions, and often accompanied by a feeling of observing oneself from an external perspective. Subjects perceive that the world has become vague, dreamlike, surreal, or strange, leading to a diminished sense of individuality or identity. Sufferers often feel as though they are observing the world from a distance, as if separated by a barrier "behind glass". They maintain insight into the subjective nature of their experience, recognizing that it pertains to their own perception rather than altering objective reality. This distinction between subjective experience and objective reality distinguishes depersonalization from delusions, where individuals firmly believe in false perceptions as genuine truths. Depersonalization is also distinct from derealization, which involves a sense of detachment from the external world rather than from oneself.