145 British Journal of Clinical Psychology (2011), 50, 145–163 C  2010 The British Psychological Society The British Psychological Society www.wileyonlinelibrary.com Clinical correlates of olfactory hallucinations in schizophrenia Robyn Langdon 1, 2,3 ∗ , Jonathan McGuire 1 , Richard Stevenson 4 and Stanley V. Catts 5 1 Macquarie Centre for Cognitive Science, Macquarie University, Sydney, New South Wales, Australia 2 Schizophrenia Research Institute, Sydney, New South Wales, Australia 3 School of Psychiatry, University of New South Wales, Sydney, Australia 4 Psychology Department, Macquarie University, Sydney, New South Wales, Australia 5 Royal Brisbane Hospital, Brisbane, Queensland, Australia Objectives. Olfactory hallucinations (OHs) are underrepresented in conventional clinical instruments, infrequently researched, and poorly understood. To advance understanding of OHs, we examined their past-month prevalence and co-occurring symptoms in two datasets. Design. One dataset comprised categorical codes and was examined using homo- geneity analysis and logistic regression; the other dataset comprised numeric ratings and was examined using principal components analyses and linear regression. Method. The two datasets included: (1) 962 cases with Present State Examination – 9th Edition (PSE-9), codes (recoded present/absent) from the World Health Organiza- tion 10 Country (WHO-10) Study and (2) 265 cases with ratings on Scales for Assessing Positive/Negative Symptoms of Schizophrenia (SAPS/SANS). Two PSE-9 items (external- and self-smells) were recoded into a single OH item to examine consistency with the SAPS/SANS dataset, which contained a single OH item. Results. Prevalence of OHs and hallucinations in other modalities differed according to the WHO-10 international centre. Across centres, OHs were present in 13% of the WHO-10 dataset, similar to the 17% prevalence rate in the SAPS/SANS dataset. Refer- ential/control delusions and other hallucinations (particularly, somatic/tactile/gustatory hallucinations) were significant independent correlates of OHs in both datasets. OHs also co-occurred with social anxiety and depression in the WHO-10 dataset, with self-smells being particularly associated with self-depreciation. ∗ Correspondence should be addressed to A/Professor Robyn Langdon, Macquarie Centre for Cognitive Science, Macquarie University, Sydney, NSW 2109, Australia (e-mail: rlangdon@maccs.mq.edu.au). DOI:10.1348/014466510X500837