When a teenager from East Baltimore was asked to describe his neighborhood, he spoke of “big rats going around in people’s trash, vacant houses full of squatters and needles on the ground.” A young woman in New Delhi, asked the same question, described the dirt and the “dirty water found lying on the roads,” while a young man in Ibadan, a large city in Nigeria, spoke of the smell of urine and streets “littered with paper and other refuse.”

All three teenagers live in the poorest neighborhoods in their communities and were surveyed as part of the “WAVE” study, a global research project that examines the well-being of adolescents in vulnerable environments around the world. Led by Dr. Kristen Mmari, an assistant professor at Johns Hopkins Department of Population, Family and Reproductive Health, the survey assessed health challenges faced by 2,400 15- to 19-year-olds from impoverished areas in Baltimore, Shanghai, Johannesburg, Ibadan and New Delhi, as well as their perceptions of their environments.

The researchers found many similarities—in all five cities, adolescents were exposed to unsanitary conditions, substance abuse and violence—but the differences between each area were especially compelling. Overall, teenagers in Baltimore and Johannesburg, despite being located in comparably wealthy countries, had far worse health outcomes and tended to perceive their communities more negatively.

In Baltimore, which is located in the world’s richest nation per capita and just 40 miles from the White House, adolescents exhibited considerably high rates of mental health issues, substance abuse, sexual risk-taking, sexual violence and teen pregnancy. In comparison, adolescents in New Delhi exhibited far fewer of those behaviors and outcomes, despite residing in a much less prosperous nation.

The reason for this, Mmari discovered, is rooted in the way teenagers interpret their surroundings. “How kids perceive their environments is really important,” she says. “That’s what’s driving many of these behaviors.” For example, a young man in New Delhi and a young man in Baltimore may both live in neighborhoods with poor living conditions and little opportunity, but because the teenager in New Delhi is able to see his environment in a more positive light, he is less likely to experience to adverse health problems. “He paints a different picture.”

But why do teenagers in Baltimore and Johannesburg have such a dark outlook? According to Mmari, one could point to a combination of environmental and social factors, including the exposure to violence and a lack of social support, which were found to be less prevalent in the three other cities.

“When you look at how they perceive their environments, kids in both Baltimore and Johannesburg are fearful. They don’t feel safe from violence,” says Mmari. “This is something we didn’t really see in other cities. In Shanghai, for example, there wasn’t a great deal of violence. You’d ask kids about their safety concerns, and they would say something like, ‘I’m afraid of crossing a busy street.’”

Community violence was a major concern for girls in Baltimore and Johannesburg, many of whom didn’t feel safe even in their own homes. Violence was also found to predict comparably higher rates of pregnancy and sexual assault in the two cities. A staggering 50 percent of 15- to 19-year-old girls in Baltimore, and 29 percent of those in Johannesburg, had been pregnant in their lifetime, and more than 10 percent of girls in both cities report being raped or assaulted by someone other than their partner in the previous year.

Adolescents in Baltimore and Johannesburg also had relatively lower levels of “social cohesion,” a phrase used to describe the emotional support provided by one’s family and neighbors. In Baltimore, many poor teens grow up in single-parent homes and have a father in prison, while those in Johannesburg tend to lose their parents to AIDS.

“In those cities, kids were much more likely to live in a one-parent household,” Mmari says. (Or, as a youth in Baltimore described it, “The kids are being raised by themselves.”) “Whereas in Delhi, most of these kids are still living in two-parent homes, so they are getting much more support.”

It’s clear we have a lot of work to do in the United States. “When you think about poor adolescents, you may instantly think of a child in Africa because there are poorer countries there, but it’s not really the country that is important,” Mmari says. “Right here in Baltimore, we have kids who are much worse off than those in African cities. The inner-city kids who are exposed to all this violence are who we should be thinking about.”