At a time when more younger people are struggling with mental-health issues, older Americans say they have fewer depression symptoms than elders of earlier generations, according to a new University of Pittsburgh study.

The study compared more than 3,000 people in four cohorts — groups born over a multi-year period — of people over 65 who lived in rural, Rust Belt communities south of Pittsburgh and were part of two long-term studies on aging and cognitive function. They were asked questions about their mood each year. The earliest group was born between 1902 and 1911. The most recent was born between 1932 and 1941 and would be 78 to 87 today. The researchers compared people who reported five or more symptoms — enough to qualify at least for “subsyndromal depression” — with those who were more content.

Depression rates dropped with each newer cohort. Compared with the 1902-1911 group, the 1912 to 1921 cohort was 43 percent less likely to have a study visit during which five or more depressive symptoms were reported. The 1922-1931 cohort was 63 percent less likely and the 1932-1941 cohort was 79 percent less likely. Nearly a quarter of people in the 1902 group said they had that many symptoms compared with 15.2 percent of the most recent group.

Lead author Kevin Sullivan, a psychiatric epidemiologist at Pitt’s Graduate School of Public Health, suspects that older people may be responding to the modern “compression of morbidity” at the end of life. That means modern health care is helping people stay healthy longer. Poor health and disability are strongly associated with depression, one reason that clinical depression is hard to measure in elders, said Sullivan, who grew up in Chester County. Even more minor depressive symptoms can affect quality of life and response to other illnesses, and raise the risk for cognitive decline, he said. That can increase medical costs.

Among people under 65, Sullivan said, depression rates are, at best, stable. He said there was not yet enough data to see whether the trend is continuing among younger seniors.

The study looked at people who lived in the Monongahela Valley, an area that Sullivan said has had continuing economic challenges and remains “medically underserved.” The analysis focused on elders from that region because they were already being studied for other reasons, and data were available.

Sullivan hypothesized that people born in later years might be more willing to admit they had depression symptoms because stigma over mental illness has declined. That is not what happened. However, he said, people now in their 70s and 80s have, as a generation, stayed healthy longer than previous groups of seniors. That means many can maintain their independence longer.

"To put it kind of bluntly," Sullivan said, "that's a reason to be happy."

Sullivan said medical professionals need to be aware of potential differences in people who were born in different eras. Today's 80-year-olds may be quite different than earlier 80-year-olds. It is also possible that different generations use different language to describe depression.

Overall, he said, depressive symptoms tend to rise slightly after age 65 as health worsens, but they drop after 85. That may be because people who live that long have little to complain about, he said. Another possibility is that cognitive decline makes it harder for many of the oldest seniors to fill out the forms.

In the study, participants were given a standard depression screening test, the mCES-D, but it was modified to make it easier. The original version of the test asks people how often they had 20 symptoms, four of which are positive, over the last week. The data Sullivan used asked only whether people had felt a particular way during most of the previous week. Some questions addressed distraction, irritability, appetite, anxiety, restless sleep, loneliness and sadness.