Thought insertion

Thought insertion is a delusion defined in the ICD-10 as the conviction that one's thoughts are not one's own but belong to someone else and have been placed in one's mind. The person may not know where the thought comes from, yet still separates their own thoughts from the inserted ones, and only certain thoughts, usually following a similar content or pattern, are felt to be inserted. The belief is held with full conviction and the person is unwilling to accept a diagnosis. It is a common symptom of psychosis and appears in many mental disorders and other medical conditions, most often schizophrenia and dissociative identity disorder. It is grouped with thought broadcasting, thought withdrawal and thought blocking as a first rank symptom. It can also be experienced by people considered nonpathological, usually in spiritual contexts or practices such as mediumship and automatic writing.