Is body chemistry the link between stress and behavior?

Plenty of research shows that certain programs can be effective in reducing aggression, depression, substance abuse and similar ills. But why these programs work is often difficult to determine.

Knowing why something works is much more powerful than knowing how to make the motor run. Understand the reason and it becomes possible to focus efforts to optimize the chances of substantial and sustained improvement.

A group of New York University researchers, led by Laurie Brotman, recently pursued an illusive why. They had already conducted a number of studies which showed that a particular preschool program could reduce behavior problems. Specifically, the program teaches parents to be loving and consistent with their children and helps children to interact in positive ways with their peers.

Having demonstrated effectiveness, the researchers wanted to know more about the underlying reasons. They were particularly interested in findings from earlier studies that suggested that the bodies of children with behavior problems function differently, particularly when they are stressed, from those of generally well-behaved children.

Children’s bodies normally show increased cortisol levels in challenging situations; there is evidence that the bodies of children with conduct disorders do not. The researchers were also interested in findings that very aggressive children have trouble understanding the intentions of their peers and thus may not respond to them appropriately.

Taken together, such findings lead to this question: Can the stress in some children's lives alter their body chemistry in such a way that they cannot accurately assess social situations and thus do not respond to them appropriately?

To begin, the researchers conducted a fairly simple experiment. They started with a group of preschool age children living in stressful homes. All 92 of them had an older sibling who had been brought to court for delinquent acts. Half of the children were chosen by lottery to participate in the program the New York researchers had previously trialled. The remaining children became the control group. The researchers tested both groups’ cortisol levels (using children’s saliva) before and after a stressful experience – entering a group of unfamiliar children.

They found that the children who participated in the program had higher cortisol levels in anticipation of entering the stressful situation than did children who did not participate. Such a finding might seem to support their hypothesis – ie, that among chronically-stressed children stress leads to body chemistry changes (abnormally depressed cortisol levels) which, in turn, lead to behavior problems.

However – and this is a big however – the researchers did not find that the kids who took part in the program who experienced increases in cortisol were generally the same kids whose behavior improved. Thus the relationship between stress, cortisol, and behavior remains unclear. – And that why remains unanswered.

•Summary of “Effects of a Psychosocial Family-Based Preventive Intervention on Cortisol Response to a Social Challenge in Preschoolers at High Risk for Antisocial Behavior” by Laurie Brotman, Kathleen Gouley, Keng-Yen Huang, Dimitra Kamboukos, Carolyn Fratto, and Daniel Pine in Archives of General Psychiatry, Volume 64, Issue 10, pp1172-1179, October 2007.

[For a more partisan slant, see also the New York University School of Medicine and Hospitals Center communications office summary Early Family Intervention Alters Preschoolers’ Biological Response to Stress [1].]