Há genes da depressão?

A depressão é genética ou deriva de factores ambientais? Provavelmente é uma mistura dos dois. E nem todas as depressões são iguais, assim como o cancro é um nome comum para várias doenças (tipos de cancro), o que torna a resposta à questão especialmente complexa:
http://www.independent.co.uk/life-style/health-and-families/healthy-living/why-is-there-no-gene-for-depression-a7291016.html


Citando:
"So is there a gene for depression? No, there isn’t. We don’t have genes for diseases, we have genes that encode proteins that serve functions in cells. So does that mean if your DNA has the relevant change in your LHPP or SIRT1 genes that you are going to develop depression? No, it probably means you may have an increased risk to develop depression depending on the environment you experience.
In the same way that we think about heart disease, cancer, obesity as having multiple “susceptibility genes”, the same is probably true for depression. "

Impacto do ambiente na saúde (estudo)

http://www.theguardian.com/society/2015/dec/18/cancer-risk-factors-environmental-study-finds
Citando:
"Environmental factors are overwhelmingly to blame for some forms of cancer, according to a new study.
Among the contributors are diet, sun exposure, UV radiation, tobacco, alcohol, the human papilloma virus and hepatitis B and C. These factors impacted between 70% and 90% of several types of cancer, including lung, colorectal, skin and cervical, said Yusuf Hannun, a cancer researcher at Stony Brook University in New York."