What’s an actual way to prove that some disease/illness is genetics?


I just don’t get why we blanket everything under genetics.. Can that actually be proven? For instance with depression, I often hear yeah it’s genetics, nothing to be done but medication. But if a parent raises a child while battling depression, how on earth would they be able to show up fully to be able to raise a healthy, emotionally supported child? If we know adverse childhood experiences and emotional neglect changes the brain, then how is it supposed to make the right amount of chemicals? So when it’s said depression is genetics, how did they actually prove that for instance?

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While your example has some problems with its assumptions, they have actually identified genetic markers for Major Depressive Disorder, bringing it out of the realm of “It seems to run in families” and into “we can test for X, Y, and Z to see if there’s a genetic component”.


Ideally you could study identical twins separated at birth. Or failing that you could count how many pairs of identical twins shared a diagnosis compared to how many pairs of non identical twins.

There are many diseases with firm genetic foundations. We know that if you have a certain mutation of a certain gene you’re much more likely to get the disease. Sickle Cell Disease and Cystic Fibrosis Liver Disease are examples.

Depression is a mental illness. Mental diseases are never as well understood as the other diseases, because the brain is much more complex than a blood cell. Whenever you read that the “cause” of a mental illness has been identified, you’re reading a ridiculous oversimplification. This is why we can’t treat mental illness as effectively as other diseases or broken bone.

There are various ways to separate the effects of genetics from the effects of environment. For example: How similar are identical versus fraternal twins? Do people who are adopted more resemble their biological parents or their adoptive parents?

For depression, the evidence indicates that genetic factors account for approximately 50% of the risk of depression, or a bit higher for more severe forms of depression.

We don’t “blanket everything under genetics.” I’m really not sure what you even mean by that. Some diseases or disorders are clearly and disputably genetic, some are very much obviously not genetic, and some have complex multifactor causes of which genetics are simply one of many factors, no single factor of which is guaranteed to trigger the disease. There’s a whole spectrum of more and less obvious genetic links to disease and more or less obviously ways to prove the link.

On one end of the spectrum, we have a disease like cystic fibrosis. It is clearly and indisputably a genetic disorder. It is caused by a specific mutation in a single gene. Every single person with cystic fibrosis has 2 copies of this gene mutation, and no people without cystic mutation have 2 copies. Every person with cystic fibrosis has a parent who carries 1 copy of the defective gene. There’s no possible other explanation except for the fact that it’s an autosomal recessive inherited genetic disorder.

On the other end of the spectrum is a disease like type 1 diabetes. There are a number of genetic mutations that are common in people with type 1 diabetes, and we know that those genes are linked to your immune system (type 1 diabetes is an autoimmune disease) and many people who have it have a parent or grandparent who also have it, but having any one or even several of those mutations doesn’t guarantee that you will develop it. Those mutations are simply risk factors.

Depression and other psychological disorders fall into the latter category. There are undeniable genetic links, such as mutations that affect chemical signalling molecules in the brain, or neuron functions in parts of the brain that we know are associated with specific psychological disorders, and the fact that these disorders tend to occur in higher frequencies in families where parents and grandparents also have similar disorders,but they’re just risk factors. They might predispose you to depression or schizophrenia or whatever else, but you might have a ton or risk factors and never develop any of these disorders because there are so many other non-genetic factors at play. Literally no one is saying that psychological disorders are exclusively genetic.

you can prove that genetics plays a role by showing that people with certain genes are more likely to have the condition (than people without that gene). Since genes do not change during one’s lifetime, we can say that genes “cause” the condtion, or rather increase the risk of it.

people who “blanket everything under genetics” refuse to take responsibility for their lives, or lives of those around them.

“Depression is because of genetics” means there is nothing you could do to end it.

“Depression increases risk of depression, but environment and thought patterns also matter a lot” means that a person can take steps to get better. It will be a long and hard journey, which is why some people try to avoid it.

Welcome to nature vs nurture at the intersection of generational trauma. Trauma can change our DNA. This is partially why overcoming poverty (trauma from stress) would infinitely help the population. It would take multiple generations to change and it would need to remain that way. I personally see some of the things like shootings as an outcome of generational trauma.

One way this is done in the mental health field is by studying twin pairs and comparing identical (monozygotic/MZ) and fraternal (non-identical/dyzygotic/DZ) twins. If a trait has a genetic basis, then identical twins will test more similarly for it while fraternal twins will have more variation. If it has more to do with “nurture” or environment, then both identical and fraternal twins will test about the same.

I actually work in research with twins if you have more questions (not a PhD so not an expert but I have some practical experience).

There are a lot of misconceptions here.
Just because a medicine is prescribed, DOES NOT mean there’s a genetic cause for the disease. Depression meds are often SSRIs which basically make serotonin in your brain last longer and serotonin helps regulate your mood.

Also, you have to acknowledge the intense complexity of genetics. I do research in genetics and it’s VERY difficult to associate genes with specific functions. We’re getting better at it and scientists have been able to find explicit markers for disease and identify the role of many genes. ‘Depression’ is a blanket term for a variety of disorders, and because it’s a mental health disorder, that makes it all the more difficult to find a biological basis for it.

And things aren’t just about genes. You don’t just gain “depression genes”. When we say there’s a genetic basis for something, that means there’s a mutation in the gene that’s causing some kind of abnormality which could be promoting the disease. It’s about how the gene is causing an underlying biological factor that is promoting depression. For example, one genetic explanation for depression of that maybe you have a mutation that causes you’re dopamine reward pathway to not work properly.

But what you’re saying about the whole environmental factors playing a role is very true. Which is why you’ll almost never hear an actual psychologist or dr tell you mental illnesses are genetic. Almost all scientists acknowledge that both environment and genetics play a role.