Odor Detection in Schizophrenia: Alternative Explanations

To the Editor: In their article published in the February 2009 issue of the Journal, Bruce I. Turetsky, M.D., and Paul J. Moberg, Ph.D., noted an odor-specific detection deficit in schizophrenia that may implicate abnormal intracellular cAMP signaling (1) . The patients were able to normally detect citralva, a strong stimulator of adenyl cyclase, but not lyral, a weak stimulator. Drs. Turetsky and Moberg failed to note prior work that conflicts with the conclusions drawn from their results.

Impaired odor detection of other substances, including iso-amyl acetate (2), dimethyl disulfide (3), and geraniol (4), has been demonstrated in schizophrenia. Individuals with schizophrenia have an impaired ability to detect geraniol, which is a strong adenyl cyclase stimulator similar to citralva. Citralva placed fourth and lyral placed 42nd in the ranking of adenyl cyclase response in tests of 44 odorants, and geraniol was the tenth most potent stimulator (5) . In a study of odorant-stimulated electro-olfactogram response, citralva ranked fifth out of 36 odorants, lyral was ranked 21st, and geraniol was ranked eighth (6) . Geraniol clearly resembles citralva in its ability to stimulate adenyl cyclase but differs in that geraniol cannot be detected normally by schizophrenia patients.

It seems that odor detection deficits in schizophrenia may have a more complex explanation than the specific signal transduction mechanism cited.