It’s no big news that for adults, depression increases heart attack risk and increases the chance of having complications or dying from a cardiovascular problem. But some fascinating new research points to the fact that childhood depression—in kids as young as 9—increases a host of health risks when those kids become teenagers. And that, in turn, carries into adulthood.

In 2004, the researchers, led by Robert M. Carney, PhD, a professor of psychiatry at Washington University in St. Louis, surveyed 201 children with a history of clinical depression. And they compared those kids to 195 of their siblings who had never been diagnosed with depression as well as 161 unrelated and undepressed kids. The average age of all the children was 9. Seven years later, in 2011, Carney and his colleagues surveyed the same kids again, looking at rates of smoking, obesity and physical activity.

The results were startling: 22% of the depressed 9-year olds were obese at 16. But only 17% of their siblings—and just 11% of the unrelated kids—were obese at 16. A third of the depressed 9-year olds were daily smokers at 16, compared to 13% of the siblings and just 2.5% of the unrelated and undepressed kids. And the pattern held for physical activity too. The 16-year olds who were exercising the least were the ones who’d been depressed at 9. The ones got the most exercise, were the unrelated kids. The depressed children’s non-depressed siblings were in the middle.

Most remarkable of all—this was true whether the depressed 9-year olds were still depressed at 16 or not.

These findings on childhood depression are cause for concern because “a number of recent studies have shown that when adolescents have these cardiac risk factors, they’re much more likely to develop heart disease as adults and even to have a shorter lifespan,” Carney said.

“Active smokers as adolescents are twice as likely to die by the age of 55 than nonsmokers, and we see similar risks with obesity, so finding this link between childhood depression and these risk factors suggests that we need to very closely monitor young people who have been depressed,” he said.