For most people, levels of the hormone cortisol spike in the morning and then decline rapidly during the day.
But when researchers looked at daily fluctuations of cortisol levels in men and women, they found that women in violent relationships often have higher-than-normal levels late in the day.
Researchers for years have suspected that the hypothalamic-pituitary-adrenal axis (HPA) regulatory system, which controls cortisol production in response to stress, is adversely influenced by violence. Says the study’s lead author Hyoun K. Kim, a scientist at the Oregon Social Learning Center and researcher in the University of Oregon psychology department:
“Existing studies have focused on the women’s HPA-axis activity only. We indeed found that women’s, but not men’s, victimization was associated with multiple indicators of diurnal cortisol levels.
It has been argued that interpersonal violence is more detrimental for women than for men, and our study suggests that it might indeed be due to disruptions in HPA-axis activity.”
Men vs. Women
Researchers analyzed cortisol from saliva samples of 122 couples during on-site assessments and four times a day— upon waking up, 30 minutes later, in mid to late afternoon, and at bedtime— over four consecutive days.
Men in the study were recruited in 1983, when they were 9 to 10 years old, for the Oregon Social Learning Center’s longitudinal Oregon Youth Study. They were drawn from mostly lower socioeconomic status families living in neighborhoods with higher-than-average juvenile delinquency.
Their romantic partners were incorporated in a separate couples’ study when the men reached 17 to 18 years of age.
The study’s duration and large community-based sample size—not just data from women seeking help at shelters as in similar studies—make for robust findings, says J. Josh Snodgrass, a biological anthropologist at the University of Oregon. He currently is studying the relationships of various biomarkers, including cortisol, to health in populations around the world.
“We think we captured a good window on the subjects’ everyday rhythms,” adds Snodgrass. “There are fluctuations, such as may occur on a very bad day, but it’s minor and on the margins; they are easy to weed out when you have four days. It’s a high-quality sample. We think it’s the environmental and behavioral pieces that are influencing the cortisol rhythms.”
The researchers say the findings show a correlation between violence and cortisol levels in women. However, they do not rule out the possibility that abnormal cortisol cycling may contribute to interpersonal violence.
“There are studies that show that dysregulated HPA axis activity is related to behavioral problems in children,” Kim says. “We cited some studies that showed that cortisol is related to interpersonal violence in men, but that finding is also based on a cross-sectional design with a very small sample of violent men and limited methods.”
The team, she says, is now looking at the women’s dysregulated daily cortisol rhythms for connections to subsequent physical and psychological outcomes to confirm a gender specific vulnerability to interpersonal violence in relationships.