Highly stressed adults who also had stressful childhoods are most likely to show hormone patterns tied to negative health outcomes, according to a new study published in the journal Psychological Science.
When stressed, our brains release the hormone cortisol; in general, our cortisol levels peak in the morning and gradually decline throughout the day. But sometimes this mechanism becomes dysregulated, resulting in a flatter cortisol pattern that is associated with negative health outcomes.
“What we find is that the amount of a person’s exposure to early life stress plays an important role in the development of unhealthy patterns of cortisol release,” said psychological scientist Dr. Ethan Young, a researcher at the University of Minnesota.
“However, this is only true if individuals also are experiencing higher levels of current stress, indicating that the combination of higher early life stress and higher current life stress leads to the most unhealthy cortisol profiles.”
For the study, the researchers looked at data from 90 individuals who were part of a high-risk birth cohort from the Minnesota Longitudinal Study of Risk and Adaptation.
The team specifically wanted to understand how stressful events impact the brain’s stress-response system later in life: Is it the total amount of stress experienced across the lifespan that matters? Or does exposure to stress during sensitive periods of development — specifically in early childhood — have the biggest impact?
Young and colleagues also wanted to study a third possibility; that perhaps early childhood stress makes our stress-response system more sensitive to stressors that emerge later in life.
The team evaluated data from the Life Events Schedule (LES), which surveys individuals’ stressful life events, including financial trouble, relationship problems, and physical danger and mortality. Trained coders rate the level of disruption of each event on a scale from 0 to 3 to create an overall score for that measurement period.
The participants’ mothers completed the interview when the children were 12, 18, 30, 42, 48, 54, and 64 months old; when they were in Grades 1, 2, 3, and 6; and when they were 16 and 17 years old. The participants completed the LES themselves when they were 23, 26, 28, 32, 34, and 37 years old.
The participants’ LES scores were grouped into specific periods: early childhood (1-5 years), middle childhood (Grades 1-6), adolescence (16 and 17 years), early adulthood (23-34 years), and current (37 years).
At age 37, the participants gave daily cortisol samples over a 2-day period. They collected a saliva sample upon waking up and again 30 minutes and 1 hour later; they also took samples in the afternoon and before going to bed.
The results show that neither total life stress nor early childhood stress predicted cortisol level patterns at age 37. Instead, cortisol patterns depended on both early childhood stress and stress at age 37. Participants who experienced relatively low levels of stress in early childhood showed relatively similar cortisol patterns regardless of their stress level in adulthood. On the other hand, participants who had been exposed to relatively high levels of early childhood stress showed flatter daily cortisol patterns — but only if they also reported high levels of stress as adults.
The researchers also studied whether life stress in middle childhood, adolescence, and early adulthood were tied to adult cortisol patterns, but they found no meaningful associations.
The findings suggest that early childhood may be a particularly sensitive time in which stressful life events — such as those related to trauma or poverty — can alter the brain’s stress-response system, with health consequences that last into adulthood.
The researchers note that cortisol is just one part of the human stress-response system, and they hope to look at how other components, such as the microbiome in our gut, also play a role in long-term health outcomes.