Eye movements and schizophrenia in Papua New Guinea: qualitative analyses with case histories

Smooth pursuit eye movement dysfunction is a psychophysiological and genetic marker for schizophrenia seen in 50-80% of patients and in about 40% of their first-degree relatives. In this study, we qualitatively assessed the smooth pursuit eye movements of 33 psychiatric patients (including 32 diagnosed with schizophrenia) and 30 control subjects in the Port Moresby area of Papua New Guinea. Brief case histories of each patient were also reviewed. Using a conservative estimate of smooth pursuit dysfunction, we found that 42% of the psychiatric patients had the marker, compared to 10% of the controls. Specific eye movement abnormalities were also much more common among the patients. A patient who had previously 'run amok' and another who was a cargo cultist had smooth pursuit dysfunction; a patient whose psychotic symptoms may have been due to cerebral malaria did not have the marker. Highland and coastal patients were similar in their expression of the marker. This study, the first of its kind done outside of large-scale, urbanized societies, provides further evidence for a common biological basis for schizophrenia in biologically and culturally diverse populations worldwide.