Much psychosis in elderly may go unnoticed. (Science News of the week).

If you get to be 85 or older, you automatically become a member of the population group known as "the very old." New data reveal that psychotic symptoms among these seniors have been greatly underestimated, a finding with potential public health consequences.

Several population studies of elderly people with healthy brains have indicated that fewer than 3 percent of them suffer from psychotic symptoms, such as hallucinations and delusions. These assessments have relied on interviews with volunteers between ages 65 and 75. So far, older individuals have rarely been studied.

The latest data, published in the January ARCHIVES OF GENERAL PSYCHIATRY, derive from interviews with 85-year-olds and their family members or other close acquaintances. In many cases, detailed medical records were also available.

This more-thorough approach found psychotic symptoms in 10 percent of a representative sample of 85-year-olds living in the Swedish city Goteborg, including those in elder-care facilities. Moreover, by age 88, the elderly volunteers with psychotic symptoms more often had developed degenerative brain disease than their counterparts had, report Svante Ostling and Ingmar Skoog, both psychiatrists at Goteborg University in Sweden.

"This is a unique and important study," remarks psychiatrist Dilip V. Jeste of the University of California, San Diego. He contends that the U.S. health-care system is unprepared to deal with a rise in mental illness as the number of elderly people increases over the next 30 years (SN: 9/18/99, p.189). What's more, Ostling and Skoog add, a cause for current concern is that many elderly people don't report their psychotic symptoms in psychiatric interviews and their condition thus evades detection by medical providers.

The Swedish researchers used census records in Goteborg to randomly select 347 participants, all 85 years old and free of neurological ailments, and then followed them for 3 years. A spouse, child, nurse, or friend described the emotional condition of 305 of the elderly volunteers to an interviewer. Medical records were available for 283 individuals.

The results provided reason for concern. In the year before the study, 35 individuals had experienced one or more psychotic symptoms, the scientists say. Symptoms included hallucinations such as hearing voices, delusions of being controlled by others' thoughts, and a pervasive but mistaken sense of being harassed or conspired against. Third party interviews provided the only information about psychotic symptoms in 21 cases.

Nearly half of the volunteers with psychotic symptoms developed a degenerative brain disease by age 88, compared with about 12 percent of the other volunteers, the researchers say.

Along with its strengths, the new study contains two weaknesses, Jeste holds. First, it doesn't address whether psychotic symptoms in elderly volunteers began early or late in life. Second, those with psychotic symptoms didn't receive a psychiatric diagnosis. Possible diagnoses cover a wide spectrum, from schizophrenia to less severe psychotic disorders.

Still, it's now apparent that physicians need to talk to third parties about the mental condition of elderly patients, says psychiatrist John C.S. Breitner of Johns Hopkins Medical Institutions in Baltimore in a comment on the new finding.