A recent study conducted by scientists from the University of Minnesota has shown that stress in childhood and adulthood has a combined effect on health and hormones.
According to findings published in Psychological Science, a journal of the Association for Psychological Science, adults who report high levels of stress and also had stressful childhoods are most likely to show hormone patterns associated with negative health outcomes.
One of the ways that our brain responds to daily stressors is by releasing a hormone called cortisol; cortisol is the body’s main stress hormone.
Cortisol level peaks in the morning and gradually declines throughout the day. But sometimes this system can become dysregulated, resulting in a flatter cortisol pattern that is associated with negative health outcomes.
Ethan Young, a researcher at the University of Minnesota, said that the amount of a person’s exposure to early life stress plays a significant role in the development of unhealthy patterns of cortisol release. He added, however, that 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.
To conduct the experiment, Young and his colleagues examined data from 90 individuals who were part of a high-risk birth cohort participating in the Minnesota Longitudinal Study of Risk and Adaptation.
The researchers specifically wanted to understand how stressful events affect the brain’s stress response system later in life. They sought to know whether the total amount of stress experienced across the lifespan that mattered, or whether it was exposure to stress during sensitive periods of development, specifically in early childhood that had the biggest impact.
According to the findings from Sciencedaily, the researchers assessed 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 rated 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 participants 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 researchers grouped participants’ LES scores 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 also provided daily cortisol data over a 2-day period. They collected a saliva sample immediately when they woke up and again 30 minutes and 1 hour later; they also took samples in the afternoon and before going to bed. Saliva samples were sent to a lab for cortisol-level testing.
At the end of the experiment the researchers found that neither total life stress nor early childhood stress predicted cortisol level patterns at age 37. Rather, 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 investigated whether life stress in middle childhood, adolescence, and early adulthood were associated with adult cortisol patterns, and found no meaningful relationships.
These 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 calibrate the brain’s stress-response system, with health consequences that last into adulthood.