New research shows that about 15 percent of young people think they're going to die early, which is why they are more likely to abuse drugs, attempt suicide, participate in other unsafe behavior—and to be diagnosed with HIV/AIDS, the Los Angeles Times reports. The study appears in the July issue of Pediatrics.

According to the survey, more than 20,000 adolescents challenge traditional wisdom that says teens participate in risky behavior because they think they are indestructible. Instead, a significant proportion of teens may take risks “because they feel hopeless and figure that not much is at stake,” said study author Iris Borowsky, MD, PhD, a researcher at the University of Minnesota.

Teens who thought they would not live long were seven times more likely than more optimistic teens to subsequently contract HIV/AIDS. Adolescence is “a time of great opportunity,” Borowsky said. “For such a large minority of youth to feel like they don't have a long life ahead of them was surprising.”