How is depression inherited? Is it a dominant trait, a recessive trait, a problem with the number of chromosomes, or something else?

Answer 1

Hi Val R.,

There are SO MANY theories for risk factors for major depressive disorder and other forms of depression. Even more confusing, people generally have multiple things that can increase their chance of developing a depression disorder. Therefore, the presence AND the severity of depression likely depends on a combination of these factors including:

1. Genetics
2. Environmental factors - your living situation, your relationships, your financial situation, even the place you live
3. Substance use
4. Other comorbid psych disorders such as anxiety and schizophrenia
5. Stressful life events or trauma
6. Your neurobiology - the way your brain is made and how it produces hormones like serotonin, norepinephrine, and dopamine.

The list goes on and is still being studies. As far as your question goes, there is NOT a strict pattern of inheritance (autosomal dominant or recessive) and there is no evidence-based chromosomal abnormality that is a standard across all cases of depression. Scientists will continue to look for one, but this is challenging because EVERYONE is very different. There are some studies showing depression inherited in some way (twin studies) - but there is not a fully described or certain pattern of inheritance. There are studies linking depression For now, we hypothesize that genes may impact your ability to deal with life stressors - your vulnerability - but do not directly cause depression.

I mostly referenced a medical reference website that is available through my hospital system, but here are some other sites you can read for a summary of these ideas!

https://ghr.nlm.nih.gov/condition/depression#statistics

http://med.stanford.edu/depressiongenetics/mddandgenes.html

Answer 2

None of the above. Depression is a very complicated disease that results from a complex interaction between both genes and environment. While there are genes known to be associated with depression, many of these are only at a few percent; what I mean by that is if you looked at genome of somebody with depression, a particular "bad" gene variant would only be found in a few percent of people with depression. Furthermore, that same "bad gene" may be found in otherwise normal people, with no effects. What I can tell you is that the genes that are associated with depression are 1) not random. Many of them are genes that encode proteins that regulate synapses, ion channels, receptors, axon targeting, and intracellular signaling molecules specific to neurons, to name a few; 2) genetically overlap with other disorders. Anxiety is well known to be comorbid with depression, but schizonphrena, attention disorders, and others also share many genetic hallmarks; 3) while there is a heritable component, most cases are sporadic, that is, they don't have any immediate relatives who have depression. This suggests that many genetic disturbances are "new"; 4) epigenetics. Changing how genes are regulated can be as disruptive -- sometimes more -- than mutations in genes. Not making enough of some proteins, but making too many of others, can have very extreme outcomes at cell, circuit, and behavior level, that are not immediately obvious or easy to predict.

I mentioned earlier that depression is an interplay between genetics and environment and you can sometimes think of environment as being "heritable" as well. People of lower socioeconomic class, those who have suffered abuse of any kind (especially early in life), lack a support system, or abuse certain drugs can all increase chance of developing depression.

It's not a nice succinct answer, but few things are simple in biology.