A groundbreaking study, by a team including University of Otago researchers, has found evidence that it is the combination of genetic factors and stressful life events that affects the likelihood that a person will find themselves depressed.
In this study the researchers looked at how the serotonin transporter gene (5-HTT) was related to depression. This gene helps to control the way that serotonin passes messages between nerve cells in the brain (serotonin is already known to be involved in depression and is the molecule that the anti-depressant Prozac targets). There are a long and a short version of this gene and as each person inherits two copies of the gene, one from their mother and one from their father, there are three possible combinations. A person can have two long genes, or two short genes, or one of each.
The results of this study showed that if there were no stressful events in their lives people suffered similar rates of depression no matter which versions of the serotonin transporter gene they had. However, for people who had a short version of the gene, the chances of becoming depressed increased as the number of stressful events increased. Whereas for people who had only the long version of this gene the chances of getting depressed didn’t change following stressful events.
The researchers also looked at whether adult depression was linked to difficulties in childhood. Again they found that it was the combination of which genes a person had and the occurrence of childhood stress which predicted depression. If there was no childhood maltreatment, then rates of adult depression were the same for both versions of the gene. People who had only the long version of the gene had the same rates of adult depression whether or not they were maltreated. However, if people had only the short version of the gene they were twice as likely to suffer depression as an adult if they were also maltreated as a child.
So for this particular gene, you can still suffer depression no matter which version you have. However following stressful events you will be much more likely to get depressed if you have a short version of the gene than if you only have long versions. Something about the long version appears to protect people from stress related depression.
Nature or Nurture?
Co-author of this research and Director of the world renowned Dunedin Multidisciplinary Study, Professor Richie Poulton says these results show that "For too long people have been fixated on the question of 'nature versus nurture', whereas this study highlights that it is 'nature via nurture' which is actually taking place. It is never simply one or the other - genes and environments constantly interact in very complex ways and only by understanding more about these interactions will any meaningful progress be made."
Get help to improve how you manage stress
This research indicates that if you are finding yourself repeatedly depressed, or notice that you get depressed in response to life events that other people seem to “take in their stride” you may have this genetic vulnerability to depression.
While we can’t at this time alter our genes, we can improve our skills for dealing with life’s stress. Collecting a broad range of strategies for both minimizing the possibility of stress, and responding more effectively to stress that can’t be avoided will be helpful. Useful strategies for reducing the impact of stress include:
- attending to your physical health and fitness
- learning relaxation techniques
- developing psychological skills such as assertiveness, thought stopping, reality checking, and mindfulness
- learning to safely experience, express and appropriately respond to all your feelings
- resolving issues related to childhood events (including major ones such as abandonment, abuse, trauma, neglect, and also more subtle difficulties such as a sense of not belonging or something about you being not okay) so that they have less influence on how you are able to respond to current emotional difficulties
- learning to be a keen observer of your own physical and emotional “early warning signs” that you are becoming stressed
Caspi, A, Sugden, K, Moffitt, TE, Taylor, A, Craig, IW, Harrington, H, McClay, J, Mill, J, Martin, J, Braithwaite, A, and Poulton, R. (2003). Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene. Science
Poulton, R. (2003). Gene Variation Increases Risk of Depression After Stressful Life Events.
http://www.otago.ac.nz/news/news/2003/18-07-03_press_release.html (downloaded 4 July 2007).
is a counsellor and psychotherapist in private practice in Auckland » more details
Article posted 5 July 2007