Dr Shock MD PhD

Almost a week ago we discussed life events and recurrence of depression. The last decades there has been a rapidly expanding research literature about genes and environment factors. They both influence different kinds of psychopathology, one of which is depression. Finding a specific gene for depression is impossible, the environment also plays an important role in depression


So what do we know about this gene and environment factors influencing depression. How do genes and environment factors work together to account for depressive disorder.

• In several twin studies family conflicts didn't increase the risk of depression in those at risk genetically speaking


• Studies with life events and genes have found more consistent results. The impact of life events was higher for those who were also at higher genetically liability of developing depression. Low birth weight has also been shown to increase the risk for them with higher genetic load. This finding has yet to be replicated.


• There is evidence of interaction between a functional genetic variant in the serotonin transporter gene and life events. Serotonin is an important neurotransmitter believed to play an important role in depression. The variant of this gene affects how much serotonin transporter protein is produced. This protein is involved in reuptake of serotonin in the synaps. Individuals with the short allelic form of this variant showed an increased risk of depression compared to those carrying the long allele but only when exposed to adverse life events or maltreatment. There have been some nonreplications, but these have been outnumbered by the number of replicated findings.


• In animals a variant of the gene for Brain Derived Neurotrophic Factor (BDNF) has been implicated to increase the risk for depression by adverse life events

Conclusion
The findings in depression of gene and environment interaction are surprisingly converging. Findings have been replicated by different research groups. Some enthusiasm about this new approach seems to be realistic.


Disclaimer
This post is based on a review article. This article addresses several different topics among which depression. This post is only about the findings with depression.


Thapar, A., Harold, G., Rice, F., Langley, K., O'Donovan, M. (2007). The contribution of gene–environment interaction to psychopathology. Development and Psychopathology, 19(04) DOI: 10.1017/S0954579407000491

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