These at-risk individuals may have weak or transient psychotic symptoms, and already show schizophrenia-like brain changes, Dr. G. Paul Amminger of The University of Melbourne in Australia, a researcher on the study, told Reuters Health. But while psychiatrists now know how to identify these individuals, he added, they don’t know what to do with them. “At the moment there’s no state-of-the-art guideline (on) how to treat those people.”

Prescribing antipsychotic medications may be helpful, Amminger added, but these medications have serious side effects, and can also be stigmatizing. “For young people they don’t want to commit themselves to a treatment which they might need to take for the next five to ten years,” he said. Furthermore, only about a third of people at high risk for psychotic disorders will go on to develop full-fledged mental illness in a given year.

In an analysis of studies from Europe, Australia, Japan and the U.S., researchers found no higher-than-normal risk of schizophrenia among people born in the nine months after the 1957 flu pandemic.

The findings, reported in the Schizophrenia Bulletin, conflict with those from some earlier studies linking the same pandemic to a heightened schizophrenia rate.