Today the NY Times published an article about a study that will appear in the Proceedings of the National Academy of Science regarding brain shrinkage in the offspring of depressed parents and grandparents. A team from Dr. Myrna Weissman program at Columbia found that people at familial-risk for depression (with a parent or a grandparent who had a history of depression) showed shrinkage of the cerebral cortex when compared to non-at-risk individuals (the lead author of this study was Dr. Bradley S. Peterson). The finding was unique to the right hemisphere, which is extremely interesting since the work by Richard Davidson and others have shown right cerebral asymmetry (more activation in the right than the left) during the processing of negative emotions and some depressive disorders.
So what does the Peterson finding mean? The findings tell us at least two things. One, the brain shrinkage occurs even if the at risk-person had never experienced depression. So this brain difference does not reflect a active “depression process”, but instead my reflect vulnerability to depression, or alternatively, a depression process at a pre-symptomatic stage. Second, the findings show that the effects appear to be limited to the right hemisphere, which gives us some interesting clues about what may be happening, and what the possible practical consequences may be of having right hemisphere atrophy.
The findings by the Dr. Weissman program are of particular interest to me because I work on a very similar, almost parallel, project. The two largest programs of familiar risk for depression are currently led by Dr. Weissman at Columbia, and Dr. Maria Kovacs at Pittsburgh. I work in Dr. Kovacs’ team on a project examining the offspring of parents who developed depression during their childhood. So our program is a bit unique in that it examines children of parents who were depressed when they were children themselves. We are currently exploring an interesting findings suggesting that these at-risk children tend to experience significantly more stressful life events when compared to non-at-risk children. This is not necessarily surprising, but we are also seeing that these elevated levels of life stressors are observed very early in the child’s life. So these at-risk kids are exposed to high levels of stress from infancy. This may be important in understanding Dr. Weissman’s findings because exposure to acute stress has been associated with brain atrophy (see for example Villareal et al., 2002). So it is possible that Dr. Weissman’s findings reflect exposure to stress among the at-risk sample, which in turn may be a key vulnerability for depression. It is possible that this factor was discussed in the paper, and I will likely make additional comments once the paper is available.
Villarreal, G. (2002). Reduced hippocampal volume and total white matter volume in posttraumatic stress disorder Biological Psychiatry, 52 (2), 119-125 DOI: 10.1016/S0006-3223(02)01359-8
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