The ‘D’ In ‘DNA’ Doesn’t Always Mean ‘Destiny’
My fellow Parents.com blogger Jill Cordes recently wrote a fascinating blog post entitled “Should Depressed People Procreate?”. Jill articulates not only her own story, but also some important points that resonate with me as a researcher (especially one who studies both genetics and depression). Her thinking is very much in line with current models of gene-environment interplay which reinforce the idea that DNA does not typically mean destiny.
Here’s the bottom line. For some rare diseases (or traits), single genes do, in a sense, act in a “deterministic” way. However, for the majority of human traits and diseases, genes are just part of the mix. The environment is critically important as well. Now while this sounds commonsense, it’s important to realize that this conclusion comes about after decades of research using a wide range of genetically-informative designs. Beyond that, over the last decade much progress has been made in studying the actual ways in which genes and environment come together. And this is where the story gets really interesting.
While there is no one gene that is known to cause depression, researchers have studied what have been called “candidate genes” – genes that biologically would play a role in the complex process of developing depression. One of these genes (sometimes called the “serotonin transporter gene” or 5-HTTLPR) has received particular attention because a number of studies suggest that variations in it (known as polymorphisms) affect how people react to stress (a key environmental risk factor for depression) – the “risk” version predicts depression in response to stress versus resilience (those without the “risk” version tend to not get depressed). However, this doesn’t mean that those with the “risk” version are destined to be depressed. In studies of adolescents, researchers have used psychosocial interventions to try to improve kids’ environments – particularly the family environment. And what seems to be happening is somewhat amazing – kids who have the “risk” version of the gene have the best response to the intervention. This has led to an intriguing idea (known as the “differential susceptibility” theory) that “risk” versions of genes don’t necessarily convey risk per se for depression and other behavioral/emotional disorders – rather they moderate sensitivity to the environment. When the environment is bad, those “risk” genes can lead to disorder. However, when the environment is good, those same “risk” genes lead to a very positive reaction to the environment.
So I was really knocked out by Jill’s thoughtful piece, as she laid out how, in her own life, she knows exactly how to take on the “bad gene” and in fact make it work for her and her family. And research certainly is backing up her approach.