Neurological soft signs discriminating mood disorders from first episode schizophrenia

Objective: To investigate the specificity of neurological soft signs (NSS) for first episode schizophrenia compared with mood disorders. Method: We assessed NSS in a sample of 60 healthy controls, 191 first episode psychosis patients and 81 mood disorder patients. We used a principle component analysis to identify dimensions of NSS. We subsequently investigated the specificity of these dimensions for schizophrenia and their relationships with medication and symptom scores. Results: We identified five dimensions; coordination disorders, movement disorders, increased reflexes, dyskinesia and catatonia. These dimensions were related to neural circuits associated with schizophrenia and mood disorders and included the fronto-striatal-thalamic and the fronto-cerebellar pathway. The movement disorder dimension, which was suggestive for the involvement of the fronto-striatal-thalamic pathway, was specific for first episode schizophrenia independent from medication. Conclusion: NSS are the result of circuitry dysfunctions rather than overall dysfunction and a particular set of NSS shows specificity for schizophrenia.