A recent study has found telltale biological markers of schizophrenia in people's noses

A reliable test for the disorder — which is believed to afflict 1 in 100 people — has long been a holy grail for psychiatrists, who lack a safe way to sample the living brain tissue. As it turns out, the olfactory epithelium, which contains neurons and their stem cells, offers a window into the central nervous system — and thus access to physical indicators of the disease. Researchers who biopsied nasal tissue in 38 individuals found that, on average, the subset of 20 who met the diagnostic criteria for schizophrenia had more of a key genetic regulator, miR-382, than did the 18 normal volunteers. The genetic difference wasn't present in all the schizophrenic participants, but because their diagnoses were based on standard clinical assessments, without biological confirmation, it's conceivable that some of them suffer from a different disease altogether. A catalog of biological correlates could make the diagnosis of mental illness much more precise and may someday replace the bloated Diagnostic and Statistical Manual of Mental Disorders. The newest edition of this bible of psychic malady is nearly 1,000 pages. To its detractors, the biblical metaphor, with its overtones of theology and prophetic logorrhea, is all too apt. Olfactory impairment is common not just in people with schizophrenia but in those at risk for it. So it makes sense that physicians may one day look into a patient's nose — rather than into a book — to diagnose the disorder.