Meta-Analysis of Olfactory Function in Schizophrenia, First-Degree Family Members, and Youths At-Risk for Psychosis

Previous research has provided compelling support for olfactory dysfunction in schizophrenia patients, their first-degree relatives, and youth at-risk for psychosis. A previous meta-analysis revealed large effect sizes across olfactory tasks but was limited to 2 olfactory tasks and did not examine moderator variables. Thus, the current meta-analysis was undertaken to incorporate additional studies, risk cohorts, olfactory test domains, and moderator variable analyses. A meta-analysis was conducted on 67 publications examining olfactory function in schizophrenia patients and 15 publications examining olfactory functioning in youth at-risk for psychosis, first-degree relatives of schizophrenia patients, and individuals with schizotypy. Results revealed medium-to-large olfactory deficits in schizophrenia patients though significant heterogeneity was evident. Several variables moderated overall study effects. At-risk youths similarly demonstrated medium-to-large effect sizes, whereas first-degree relatives and individuals with schizotypy showed small effects. Findings suggest robust olfactory deficits in schizophrenia and at-risk youths. In schizophrenia, several variables had significant impact on these deficits and warrant consideration in prospective studies. Our findings also indicate that olfactory measures may be a useful marker of schizophrenia risk status.