Childhood Adversity Predicts Depression in Adulthood?

Two articles in the February issue of Archives of General Psychiatry explore the connction between trauma in childhood and depression in adulthood–on a molecular level. In one study (Bradley et al) researchers examined a gene for a hormone (CRH) in almost 500 persons. CRH acts in the body to set off a whole cascade of stress responses, most importantly: cortisol, the “stress hormone” par excellence. They found that individuals with particular variations in this gene who had been abused were more likely to have depression problems. In other words, particular variations of this gene make if more likely that a person will develop depression if they are a victim of abuse. This is supportive evidence for several theories about causes of depression: 1) An interaction between genetics and environment is responsible for depression, and 2) The stress hormone cortisol is an important factor in the development of depression.

In the other study, ( Ouellet-Morin et al ) 346 pairs of twins were evaluated at 19 months of age. The children were exposed to a mildly stressful situation (having the child and his mother sit in a room into which a women dressed as a clown enters and talks to the child) and the change in the childs’s cortisol level before and after the incident was measured by testing a sample of saliva. The researchers found that a more exaggerated change in cortisol level occurred in the children in which there was some evidence of stress at home (e.g., low income family, single parent household.) It’s interesting to note that in the “stressed” twins, there was no difference between the monozygotic (identicle) and dyzogotic (fraternal) twins. This is interesting because one would expect that there would be a difference in the different kinds of twins if genetics (rather than the stressful environment alone) were the cause of the exaggerated stress response.

Thus, we have a bit of a contradiction between the two findings: the first study found genetic differences in a cortisol-related gene put people at risk for depression, the second found that environment was the more important factor in determining who would develop the exaggerated stress response that is thought to lead to depression. One possible explanation is that there were not enough identical twins in the study to be able to pick up the difference between twin types (the issue of the power of the study.)

The take-home message: Childhood adversity is very likely to be an important risk factor to depression