New research suggests that experiencing discrimination during adolescence can have a lasting impact.

A team of researchers led by Northwestern University found that feelings of discrimination can adversely affect with the body's levels of the primary stress hormone, cortisol, in both black and white people. In African-Americans, however, the negative effects of "perceived discrimination on cortisol are stronger than in whites," The Siasat Daily reported.

"We found cumulative experiences matter and that discrimination mattered more for blacks," Emma Adam, lead author of the study, said in a statement. "We saw a flattening of cortisol levels for both blacks and whites, but blacks also had an overall drop in levels. The surprise was that this was particularly true for discrimination that happened during adolescence."

They also found that the teenage years are a particularly sensitive period to be experiencing discrimination, in terms of the future impact on adult cortisol levels.

In times of stress, the body releases several hormones, including cortisol. Ideally, cortisol levels are high in the morning to help energize us for the day. At night, cortisol levels wane as the body prepares for sleep. Work by Adam and others suggests that young adults from racial/ethnic minority groups who perceive more discrimination have higher levels of cortisol in the evening and less decline in cortisol levels across the day than those with lower discrimination.

Having flatter or dysfunctional cortisol levels across the day is linked with higher fatigue, worse mental health, cardiovascular disease and mortality, as well as cognitive problems, such as impaired memory.

For the study, researchers collected and analyzed data over a 20-year period. They measured discrimination from ages 12 to 32, prospectively. They also assessed adult cortisol levels over a seven-day period. Their analysis showed that the more discrimination people experience throughout adolescence and early adulthood, the more dysfunctional their cortisol rhythms are by age 32.

"There's a fair amount of research on how discrimination affects people in the moment. But we haven't been sufficiently considering the wear and tear and accumulation of discrimination over lifetimes. Our study offers the first empirical demonstration that everyday discrimination affects biology in ways that have small but cumulative negative effects over time," Adam said. "Even after controlling for income, education, depression, times of waking and other health behaviors, they still couldn't explain or remove the effects of discrimination, "making it unlikely that those other factors play a role."

The findings are detailed in the journal Psychoneuroendocrinology.