Why is there no depression gene?

Depression is sometimes categorized as a mental, rather than a physical illness…[but d]epression does run in families, which could mean depression is genetic, an inherited condition. But families don’t just share genes – they also experience a similar environment. So how can we separate genetic influences on depression from environmental factors?

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Analysis in 2005 of a large number of twin studies indicated that around 40% of the risk of developing depression is genetic, and the remaining 60% associated with non-shared environmental factors. It is therefore too simplistic to say…depression [is] either genetic or environmental.

Given that depression, like cancer, is not one single illness, it is perhaps not surprising that a single gene for depression has not been found.

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[The psychiatric genetics consortium group] concluded in 2015 that most of the genetic effects found so far…are not very reliable or robust. But this…just means we haven’t really done the right studies yet….

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In the same way that we think about heart disease, cancer, obesity as having multiple “susceptibility genes”, the same is probably true for depression.

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