How are mental disorders inherited?

And that’s where we need to begin…

How does heredity work?

So I need to explain the following concepts first: - Heredity - Genetic - Familial

To answer your question properly, I need to explain each of these terms. Are you up for a crash course in genetics? (It’ll be fun, I promise!)

A crash course in genetics

Heredity is basically the passing on of characteristics (or traits, as they’re properly called) from one generation to another, most often in the context of parents to their children. You know how we say things like, “I have my father’s nose, but my eyes are from my mother”? Yep. That’s heredity we’re talking about right there.

Genetic has to do with genes which, as you know, are the means by which the characteristics are transferred. So while heredity is about what is transferred, genetic is about how. If you have your father’s nose, it’s because you have some of his genes.

Familial is the one you might find a little less familiar (haha!) than the rest, but it’s pretty straightforward: it simply means a particular characteristic or trait is within a family. You know how in some families you find cousins who share a look, sometimes so much you might even mistake them for siblings? Exactly.

You get the three now, yeah?

Now I need to mention here that although I’ve been referring to obvious traits, like eyes and noses and facial appearance, what we’re talking about actually cuts across every single thing. That includes our physical appearance and the function of your internal organs, to how we think and behave (good and bad). It even includes the illnesses a person may be prone to: from hypertension and diabetes and various cancers, to sickle cell and asthma and arthritis.

Everything is coded in the genes.

[bctt tweet="Everything's coded in our genes. Discover the causes of mental disorders…" username="DocAyomide"]

And that means everything, ultimately, is genetic. Including mental illnesses.

But — and this a very big but — the operational word there is “ultimately.” And that brings me to where I need to explain a little more about the genetic part I mentioned earlier.

How genes work (crash course of the crash course)

Remember what I explained earlier about having the features of one or both of your parents? And I explained how genes are responsible for that, because they carry the blueprint (DNA) for a number of traits. And we often think of diseases as being transferred like that too, but they aren’t.

Not mostly, anyway. You know how sickle cell disease is transferred in a very straightforward way: a person with the sickle cell gene transfers it directly to their children. Well, that’s exactly NOT how the transfer of mental illness works. No, it’s more complex. Instead of one gene carrying any particular mental illness, say depression, what we tend to see is many associated genes. Note: associated genes.

Allow me to illustrate this complexity with a familiar picture. You know that thing Nigerian parents do where a teenage child starts to “misbehave” and they say it’s one particular friend that affected him? That’s like blaming something on one gene, and sometimes that’s the case.

Sometimes, however, it’s not that simple. Instead of one friend, it’s many different friends and various experiences (including from home itself) contributing to the change. In fact, there are times, when, if you’re honest, you can’t even really point to anything in particular.

It may be more correct, therefore, to say the friends are associated with the change. But it would be wrong (as well as unfair) to go all out and say they caused it.

And that’s pretty much what happens in mental illnesses (and a lot of other illnesses too, actually, including hypertension, diabetes and most cancers). It’s not ONE gene, it’s many genes associated with the illness. To make things even more “interesting,” we can’t often say how much each particular gene contributes to the problem, or exactly how they’re transferred.

So is mental illness inheritable?

You can see now why my original short answer was, “Yes and no,” right?

I really wasn’t trying to confuse you, just that they way inheritance works is rather complex. And when we oversimplify it, we actually help make life a little worse for people who live with it, and those who care about them, because we create a level of fear that they don’t need.

But now that you understand it, here’s a better short answer:

Yes, mental illness is genetic. No, it’s not hereditary.

Make sense now? Cool.

Now go explain it to someone. No, really. I’m not even kidding. Teaching it will: - help you be sure you get it, because teaching is one of the best ways to learn. - also help you remember it, because teaching is one of the best ways to remember. - help spread the word, and contribute to making life better for people with mental health conditions.

And that’s if you teach just one person. Imagine teaching even more.

Coming soon: part two of this — it’s myth-busting time! Plus, I'll address the question of getting married into a family with a history of mental illness.