Researchers at Johns Hopkins University School of Medicine have published a study entitled “Chronic Corticosterone Exposure Increases Expression and Decreases Deoxyribonucleic Acid Methylation of Fkbp5 in Mice,” Endocrinology, September 2010, in which they claim to have identified a possible epigenetic cause of depression and other mood disorders, including bipolar disorder. For a more layman’s account of the study and its conclusions, I recommend the Johns Hopkins press release entitled “Chronic Stress May Cause Long-Lasting Epigenetic Changes.”

The prefix epi- means outside, above, over, or on top of. The term epigenetic refers to factors outside the fundamental gene structure that affect a gene’s expression. In this study, researchers examined the effects of a common stress hormone on a gene that has been linked to mood disorders and found that “… long-term exposure to a common stress hormone may leave a lasting mark on the genome and influence how genes that control mood and behavior are expressed.”

Moreover, this effect can be passed onto the next generation – so if a mom is exposed to chronic stress and this affects her mood-related genes, the “stress effect” on the gene, not just the gene itself, can be passed on to a child. In other words, a child’s likelihood of eventually exhibiting depression or other mood disorders is affected not only by her own genes and her own stress but also by the stressors that her mother was exposed to. This is a fascinating evolution of our understanding of how genes and environment interact to cause illness.

This study is of practical value in two ways:

  • It may help in developing a clearer understanding of the causes of depression and bipolar disorder, which will help in developing effective medications that specifically target the chemical “marks” that are left on genes by stressful experiences.
  • It serves as another reminder of the importance of managing stress – to possibly prevent the onset of depression and bipolar and possibly help in maintaining mood stability. This is important for our own health and for what we pass on to our children.

Many questions surround the issue of how nature and nurture team up to cause illnesses such as depression and bipolar disorder, but a growing body of scientific data demonstrates and helps to clarify the biological basis of these interactions.