Or the link to mental health more broadly.
A team of British researchers worked on finding a correlation and isolated a gene that appears to be prevalent in multiple family members with depression.
The chromosome responsible for all this is 3p25-26 and it was found in over 800 families where depression was recurrent. Part of the conclusion was that as many as 40 percent of those with depression can trace it to a genetic link. The rest of the 60% is down to other factors, like the environment and factors outside our control.
There’s also another correlation which showed that those with family members (parents or siblings) who have depression are up to three times more likely to also be depressed. This however can be explained genetically or due to environmental factors.
Gender might also play a role. Though the extent to which nature or nurture play the bigger part here is unclear. There’s one study (published in Psychiatry Online, I can’t find it now), which found that women had a 42% chance of hereditary depression, while men had only a 29% chance.
Then there’s the serotonin link. That’s why SSRIs (selective serotonin reuptake inhibitors) work, although no one really knows exactly how they work. Serotonin is the “feel good” chemical. It is thought that an imbalance in serotonin can lead to mood disorders, depression, anxiety, and a series of other mental health issues. There are quite a few theories about the serotonin-depression link, and serotonin continues to be studied as the key to the hereditary aspect of depression.
This is a good summary you can read more on:
Also check out these 2 studies: