The whiff of a sensuous perfume, the scent of a washed and powdered baby, the aroma of a steak on the grill—such smells help bring people together and bond them. In fact, olfaction and social affiliation are related in most mammals.

Thus, it should probably come as no surprise that the difficulty in identifying odors that many patients with a schizophrenia-spectrum disorder possess has been linked to the lack of a social drive that many also possess.

The finding comes from Dolores Malaspina, M.D., a clinical research psychiatrist with the New York State Psychiatric Institute, and Eliza Coleman, Ph.D., a New York University psychologist. Malaspina presented the discovery at the Ninth International Congress on Schizophrenia Research, held in Colorado Springs, Colo. It will also be published in the June Archives of General Psychiatry.

"This is an important finding, and it fits in with other data," Lili Kopala, M.D., told Psychiatric News. Kopala is a clinical professor of psychiatry at the University of British Columbia and a pioneer in olfaction-schizophrenia research.

Malaspina and Coleman gave a smell-identification test to 70 subjects with a schizophrenia-spectrum disorder—that is, 70 persons who met DSM-IV criteria for either schizophrenia or for schizoaffective disorder—and to 68 healthy controls. They found that the schizophrenia-spectrum subjects were, on the whole, considerably impaired in olfaction ability compared with the controls, although there were variations among the subjects. This finding did not surprise them since olfaction deficits have been identified previously in a number of patients with a schizophrenia-spectrum disorder. In fact, Kopala is believed to be the first scientist to report such deficits, in 1987. What Malaspina and Coleman wanted to learn, however, is whether there is any link between smelling difficulties in the schizophrenia-spectrum disorders and the possession of various positive symptoms, negative symptoms, depression, or lower intelligence often stemming from these illnesses. Thus, the researchers gave a battery of tests to their schizophrenia-spectrum subjects to determine whether they possessed such symptoms. Then they looked at the data to determine whether they could make a connection between possession of any of these symptoms and smell-identification scores.

The researchers found a statistically significant link between lower intelligence and smelling difficulty and a statistically significant link between impaired social drive and smelling difficulty. Both links were independent of each other. And while intelligence explained 25 percent of the variance in smell-identification scores in schizophrenia-spectrum subjects, social drive explained another 23 percent of the variance. Thus, both intelligence and social drive together explained almost 50 percent of the variance.

It is the link between impaired social drive and smelling difficulty that especially intrigues the researchers because smelling and social bonding are so intimately connected in humans and other mammals.

The finding raises a host of fascinating questions. For instance, in the schizophrenia-spectrum disorders, might there be common neural bases between impaired social drive and olfaction difficulty? Do these common bases go awry early in life? After all, many schizophrenia scientists believe that schizophrenia is a neurodevelopmental disease. Also, could the level of difficulty that a schizophrenia-spectrum patient has in smelling reflect how much trouble he or she has in connecting to people?

Finally, does the finding have any implications for human evolution? Malaspina thinks it does. "The brain systems that evolved to process odors may be the very same brain systems that evolved to manage social relationships," she told Psychiatric News.

The study was financed by the G. Harold and Leila Y. Mathers Charitable Foundation, National Alliance for Research on Schizophrenia and Affective Disorder, and the National Institute of Mental Health. ▪