Smells like schizophrenia

Bruce Turetsky in the hermetically-sealed chamber used to conduct scent-identification tests. The device behind him prepares the scents.

Photo by Daniel R. Burke


To get a better understanding of the origins and causes of schizophrenia, Assistant Professor of Psychiatry Bruce Turetsky and colleagues in the School of Medicine followed their noses and sniffed out some intriguing information.

Building on research that is producing clues about how schizophrenia affects the brain, Turetsky used a smell test developed at Penn to study how well schizophrenics could identify scents and objects based on their smell.

As it turned out, the patients with schizophrenia didn’t smell well. While they could process visual cues as well as normal subjects, they did far worse on the olfactory ones.

“Their ability to recognize an object based on its smell was worse than their ability to identify an object through pictures,” Turetsky said.

The Penn researchers then followed up this research by conducting the same test on normal siblings of the schizophrenic and non-schizophrenic subjects. As with the subjects themselves, the siblings of the schizophrenic subjects did worse than their normal counterparts. Furthermore, the schizophrenics had smaller olfactory bulbs — the chamber in the nose that receives odors — than the normal control subjects.

“This suggests that the smell deficit is inherited along with the vulnerability of schizophrenia,” Turetsky said. “And it spurred us on to look more at the underlying brain systems.”

There, they found a similar reduction in the size of the lobes that process smell data, with the control subjects having the largest lobes and the schizophrenics the smallest, with their siblings in between.

This suggests to Turetsky that schizophrenia may be the result of arrested development in the brain’s olfactory region, which is also the region that processes emotions, another area where schizophrenics show a deficiency.

“The brain stops developing synapses around age 12, but the olfactory regions continue to develop throughout life,” he said. “We think it’s that process of how the brain develops that got messed up during development in the womb.”

If Turetsky is correct, this would give researchers the first physiological clues to the origins of schizophrenia. To follow up on this work, Turetsky and his colleagues are now measuring the olfactory bulbs of the normal siblings of schizophrenics to see if the physical link matches the neurological one.

But while this research offers tantalizing clues about the causes of schizophrenia, it’s not likely to lead to new treatments anytime soon. “We don’t really know what the underlying abnormality is,” he said. “[This research] could help identify the genes involved in the disease, and that could have an effect on future diagnoses. But that’s way down the line.”

Originally published on October 26, 2000