Stress has combined impact on hormones and health, study says

Adults with high levels of stress who also had stressful childhoods are more likely to show hormone patterns typically associated with negative health outcomes, according to a new study published in the journal Psychological Science.

The study used a longitudinal sample of 90 adults followed from birth to 37 years old in the Minnesota Longitudinal Study of Risk and Adaptation. One way the brain responds to stress is by releasing the hormone cortisol, with levels typically peaking in the morning and declining throughout the day. If the system is dysregulated, cortisol levels can fluctuate, which is associated with negative health outcomes, researchers said in a statement released by the Association for Psychological Science.  

Researchers examined three models of the effect of stress exposure on diurnal cortisol: the cumulative model, the biological-embedding model, and the sensitization model, according to the study abstract. The cumulative model focuses on cumulative life stress, whereas the biological-embedding model implicates early childhood stress, and the sensitization model posits that current life stress interacts with early life stress to produce flat diurnal cortisol slopes, researchers said.

The team assessed data from the Life Events Schedule (LES), which surveys individuals' stressful life events, including financial trouble, relationship problems, and physical danger, and mortality. Scores were grouped into five specific periods based on age, the study said.

At age 37, participants also provided daily cortisol data over a two-day period. They collected a saliva sample immediately when they woke up and again 30 minutes and one hour later and took samples in the afternoon and before going to bed. Saliva samples were sent to a lab for cortisol-level testing.

Researchers found that neither total life stress nor early childhood stress predicted cortisol level patterns at age 37. Cortisol patterns depended on both early childhood stress and stress at age 37, researchers said. Participants who experienced lower levels of stress in early childhood showed 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 fluctuating daily cortisol patterns, but only if they also reported high levels of stress as adults.

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 calibrate the brain's stress-response system, with health consequences that last into adulthood, researchers said.

Further studies are needed, but researchers say they hope to investigate other components of the human stress response system, such as the gut microbiome, and how they affect long-term health outcomes.