Wealth typically begets health, as researchers have known for decades. Lower-income families have more medical issues during early childhood and adulthood than wealthier families do. Infants are more likely to be born premature and underweight. Children have higher rates of asthma. Adults are at higher risk of diabetes and cardiovascular disease.

Such disparities among teenagers, however, whose health problems tend to be subtler, had been harder to pin down. According to a new study by researchers at McGill University's Institute for Health and Social Policy, the socioeconomic fault line divides adolescents, too. Increasingly, low-income youths suffer from more physical and psychological issues than their more affluent peers, which could reverberate well into adulthood.

The trends emerged from data in the Health Behavior in School-Aged Children study, a survey-based analysis conducted every four years and led by the World Health Organization. Using surveys completed in 2002, 2006 and 2010, the McGill team examined reports of physical well-being, psychological health and family affluence among nearly 500,000 students—ages 11, 13 and 15—in 34 countries in Europe and North America. Entries were matched with the Gini index, an estimate of national income inequality.

Published online in February in the Lancet, the analysis uncovered a growing health gap between teenagers in wealthier and poorer households. Disadvantaged adolescents reported less physical activity and more bodily aches and pains, sleeplessness, and emotional difficulties, such as nervousness and irritability, compared with more advantaged teenagers. The gulf grew wider in countries with more economic inequality. “The U.S. was consistently one of the most unequal countries in terms of health,” says psychologist Frank Elgar, lead author of the study.

Potential solutions to this escalating problem cover a wide swath. Karen Matthews, who studies adolescent health at the University of Pittsburgh, recommends more sleep—with earlier bedtimes or later school starts—in light of studies linking diminished shut-eye with a higher risk of obesity in teens. Because physical activity improves weight control, mental alertness and grades, schools should also consider reversing the trend of cutting gym time.

Other experts lobby for the integration of “social medicine”—treatments that recognize the social factors contributing to disease and illness—into physician training. Harvard Medical School now has a semester-long course in that vein. Similarly, the American Academy of Pediatrics issued a policy report in 2012 on the need to halt poverty-driven health disparities during childhood, before they fester and lead to life-threatening adult diseases.

The earliest interventions may be most effective. Research by James Heckman, an economist at the University of Chicago, found that programs for ages younger than three years, such as nurse home visits to assist new parents, yielded the greatest dollar-to-dollar return on investment in terms of helping disadvantaged youth attain the education and employment levels necessary to improve their socioeconomic status later in life, in comparison with fixes such as job training after high school.

Any and all approaches may be warranted, considering the high stakes for individuals and society. “If you are unhealthy as a teen, it's very likely you'll be unhealthy as an adult,” Matthews says. And we can all agree that adolescence is already tough enough.