Depression: Biological Causes - Genetics

If you ask someone with depression if they have a family member with a history of a depression, the answer will most likely be, “Yes.”  That’s because depression tends to run in families.  The question then becomes one of Nature vs. Nurture, “Does depression run in families because family have similar genes or because family members grow up in similar environments?” It turns out that the answer is a little bit of both.
 
Nature vs. Nurture  in Depression
To understand the “Nature” of depression, it is important to know that we inherit half our genes from our biological mother and half our genes from our biological father.  Genes are like the “blueprints” of life and tell the cells in our bodies what to build and how to work.  They determine our height and eye color and also help to create our personalities.  However, our environments can influence our genes.  For example, a son of two basketball players may have genes that tell his cells to grow his adult body to 6’6”, but if he doesn’t have regular access to food or his mother drank alcohol excessively during her pregnancy, he may only grow up to be 5’10”.  These “gene by environment” interactions are very common so it is very unusual for experts in the genetics of depression to say that it’s one or the other.
 
Is there a gene for depression?
No.
 
Just as researchers have identified single genes that are responsible for certain diseases such as Cystic Fibrosis or Down Syndrome, researchers have attempted to identify a “depression gene.” So far they have not found consistent results.  Because mental health disorders like depression are complex and look very different from one person to the next, it is almost certainly the case that there are multiple genes acting together that contribute to a person’s overall genetic vulnerability to depression.