By Julie Deardoff
Feelings of discrimination can change how our bodies control levels of the stress hormone cortisol. That’s true for both whites and blacks, but new research suggests African Americans are especially vulnerable, particularly teenagers.
Data collected during a 20-year period show that the more discrimination people experience throughout adolescence and early adulthood, the more dysfunctional their cortisol rhythms are by age 32.
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.
Previous research indicates that discrimination can affect the natural rhythm of this process. 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 who perceive less discrimination in their lives.
Having flatter or dysfunctional cortisol levels throughout the day is linked with fatigue, cardiovascular disease, and impaired memory.
“We found cumulative experiences matter and that discrimination mattered more for blacks,” says study lead author Emma Adam, a developmental psychologist at Northwestern University’s School of Education and Social Policy.
“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.”
Adams says adolescence might be an important time period “because there are a lot of changes in the brain and body. When you experience perceived discrimination during this period of change, it’s more likely that those effects are built into the system and have a bigger impact.”
The researchers measured discrimination from ages 12 to 32, prospectively. They also assessed adult cortisol levels over a seven-day period. Using modeling, they determined the age range during which discrimination most dramatically affected cortisol. 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,” Adam says.
“We’ve been trying to solve the mystery behind why African Americans have flatter diurnal cortisol rhythms than whites,” Adam says.
“There’s a fair amount of research on how discrimination affects people in the moment. But we haven’t sufficiently considered 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.”
The findings appear in the journal Psychoneuroendocrinology.