Comparison of Ketamine-Induced Thought Disorder in Healthy Volunteers and Thought Disorder in Schizophrenia

OBJECTIVE: This study sought to determine whether thought disorder induced in healthy volunteers by the N-methyl-d-aspartic acid (NMDA) receptor antagonist ketamine resembles the thought disorder found in patients with schizophrenia. METHOD: The Scale for the Assessment of Thought, Language, and Communication was used to assess thought disorder in healthy volunteers (N=10) who received subanesthetic doses of ketamine and in a group of clinically stable inpatients with schizophrenia (N=15) who did not receive keta­mine. RESULTS: Mean scores on the Scale for the Assessment of Thought, Language, and Communication for patients with schizophrenia and healthy volunteers receiving ketamine did not differ significantly. Moreover, three of the four highest rated test items in both groups were the same. CONCLUSIONS: These data suggest that ketamine-induced thought disorder in healthy volunteers is not dissimilar to the thought disorder in patients with schizophrenia and provide support for the involvement of the NMDA receptor in a cardinal symptom of schizophrenia.