What is the term for the condition where an individual believes they have multiple personalities?

The term for the condition where an individual believes they have multiple personalities is Dissociative Identity Disorder (DID). This psychological condition is characterized by the presence of two or more distinct personality states or an experience of possession, which can significantly impact a person's sense of self and daily functioning. DID often arises as a coping mechanism in response to trauma, particularly during early childhood, allowing the individual to compartmentalize the traumatic experiences.

This disorder differs from others like Borderline Personality Disorder, which is characterized by unstable moods, behavior, and relationships but does not involve multiple personalities. Complex Post-Traumatic Stress Disorder refers to a subset of PTSD symptoms developed over prolonged trauma, without the presence of distinct identity states. Narcissistic Personality Disorder involves a pervasive pattern of grandiosity, need for admiration, and a lack of empathy but is unrelated to the experience of multiple identities.

Understanding Dissociative Identity Disorder involves recognizing its roots in trauma and the complexities of identity, making it a unique and significantly different diagnosis from the others listed.