Natural Selection

Going on the assumption that behavior are linked to genes, then genes would be able to be traced back through heredity, right?

But if that was really the case.. then how would you explain all the mental health problems? Take depression for example (non-situation depression that is). If you're depressed, then you have less likely of a chance to produce offspring, and less likely of a chance to pass your "depressed" genes down to someone else right? The whole survival of the fittest thing..

So then how can you account for how many people are depressed? Does that mean that behavior really doesn't have a lot to do with genetics? And if thats the case, then really, the whole genetic passing of mental health issues doesn't really make sense?

I'm not trying to offend anyone.. i struggle with depression myself... i'm just trying to scrap together some ideas.

Any thoughts?

That's a natrual assumption traci. However, genetics are much more complicated than that. Because not every trait is passed down and because somethings are recessive and other traits are dominant. Not to mention that many depressed people do have children. They might be less likely but depressed people usually have some periods of time in their life when there not depressed and when they do normal everyday things. Like having offspring.

But we will probably never know for sure how much is genetic and how much is enviromental. Like is a daughter depressed because she lived in a home with depressed people or was she born with that trait?

Huh, I’ve never thought about it in these terms before. It does seem to defy the rules of Natural selection to perpetuate behaviors that are detrimental to our species, but we seem to do it don’t we.

That is a really interesting question - quite a literature has been generated on that.

One assumption (that might be false) is that the behaviours that constitute mental disorder constitute an evolutionary dysfunction. That is to say that the behaviours that constitute mental disorder constitute a reduction in evolutionary fitness (survival and reproduction). That assumption might be false. In order to assess it one could see whether people who have the experience of depression tend to live less long (on average) or - more importantly - whether they have a reduced number of offspring. It is quite tricky to assess whehter there is a reduction in evolutionary fitness or not.

One could take another line (a number of theorists have) that instead of mental illnesses constituting dysfunctions they constitute adaptive strategies (that increase evolutionary fitness). This could be so if we evolved to be optimal in earlier environments (living in smallish hunter gatherer groups of around 30 people). In that kind of environment depression might have elicited appropriate caregiving by others. In current environments (much larger societies) it might be that depressed behaviour doesn't serve its adaptive function of eliciting caregiving from others.

Another notion is that depression itself might constitute a dysfunction but that some trait that is linked to depression (sensitivity or creativity or something like that) might constitute an evolutionary function.

Lots of controversy...

One thing that is done to find out how heritable a trait is (how 'genetic' it is) is linkage analysis. That involves going back through family trees and looking at incidence of a particular disorder. That is how we find that some disorders are dominant, or heritable but recessive or whatever. It seems as though mental disorders aren't going to have a simple genetic basis, however. The best candidate for a genetic basis of schizophrenia involves 3 values across 3 different genes. They found that through linkage analysis of data from the icelandic genome project. We know that the genetic basis of schizophrenia isn't very robust, however, because if one twin has schizophrenia it is more likely than not that their genetically identical twin won't have it...

Schiozphrenia has been linked to creativity. Schizophrenia has also been linked to religious leadership, seers, holy leaders, prophets, healers etc. It might be that schziophrenic symptoms (some of them) such as delusions, hallucinations, mania were positively valued in past societies (and in some current day societies) whereas in western culture they are disvalued such that people are labelled and stigmatised as disordered...

by the way... the best argument against mental disorders being evolutionary dysfunctions is precisely the one you gave: one wouldn't expect heritability to be as high as it is if the traits were malfunctional. That has been what has driven alternative explanations (the traits being evolutionary adaptations, or adaptations to past environments, or whether they are an unfortunate bi-product of another trait that does have adaptive value)

I was lost on your assumption that depressed people wouldn't have a chance to reproduce as much. People don't behave entirely by instinct/genes like other animals do or mostly do, they can go against their genetic tendencies where behavior is concerned. Inheriting an aptitude for music or art does not mean we have to become muscians and artists in the same way that inheriting brown eyes means we are stuck with brown eyes.

> I was lost on your assumption that depressed people wouldn't have a chance to reproduce as much.

It isn't my assumption (I would bet that it is empirically false - though that would of course be speculation since one would need to do a study to know).

It is an assumption behind the view that depression constitutes an evolutionary dysfunction. This is a view that is popular. Especially with Jerome Wakefield - and it is cited in the majority of textbooks on abnormal psychology and psychiatry. To say that x constitutes an evolutionary dysfunction is just to say that if you take the people with x they will survive and reproduce (on average) less than those without x. Not in every particular case (evolutionary fit individuals sometimes get struck by lightening - which is to say that there are other forces in play such as genetic drift). But to say that x is an evolutionary dysfunctioning trait kind of is to say that one would expect its frequency to lessen in the population over time. Whereas rates of mental illness are on the increase...

And that needs explaining.

I think that over time our concept of mental disorder has expanded to embrace more and more people...

A concept that was originally reserved for people who needed to be physically restrained to prevent their endangering themselves or others...

Has come to be applied to people who express dissatisfaction with their lives. Those people once would seek assistance from clergy. Now they go on prozac.

Once upon a time you had to have A or B or C to count as having a mental disorder (for example)

Whereas now you have to have A or B or C or D or E or F or G or H...

So... It isn't so surprising that more people would qualify as having one.

Whereas people who had extremely florid delusions for much of their life, depression such that they were catatonic etc probably WERE at a survival / reproduction disadvantage...

It is less clear that a single episode of existential angst constitutes an evolutionary dysfunction.

Thats what I don't understand, how mental illness are increasing...

Going with this whole evolutionary theory, if someone is say Depressed, or anxious, or whatever... chances are they would be less motivated to go out and build relationships and have a family (hypothetically). So over time.. it would make sense that their genes would have LESS of a chance to be passed on than someone who is say not depressed.

Then again, I suppose there is the whole nature vs nurture debacle, and situations can arise that would cause certain people (people who maybe wouldn't have a predisposition to become depressed), to actually become depressed. In that case, it wouldn't be a matter of heredity per se, but the situational factors that could be of contribution.

Maybe thats one of the reasons mental illness's are on the rise ...

That is a good point too Alex... and maybe also, people could just be more "willing" to acknowledge their "illness" and do something about it.

I mean, if you take a look at my family history for example, I personally think there's a HUGE line of depression, but at that point, no body talked about it. Nothing was done about it because it was just seem as a sort of taboo.

But I guess what I am doing here is questioning the idea that there is a robust relationship between certain genetic values and certain behavioural traits (those involved in mental illness).

I guess I think that social causal mechanisms are likely to be more robust than genetic causal mechanisms at the end of the day. The trouble is that we are more limited in finding out about social causal mechanisms than we are in finding out about genetic causal mechanisms because of practical and ethical constraints around manipulating aspects of society vs manipulating genes and / or neurology in rats.

The more i think about it, the more i agree that social mechanisms have a significant influence; if for nothing more, than context causing retrieval-generated priming. The more exposure you have to a certain stimuli (environmental), the more likely there is to be a direct influence as oppose to an implicit genetic inheritance.

Part of the problem is that inter-rater reliability is poor. That means that if you were to film a person (for example) and then show it to lots of different clinicians, then those clinicians would disagree a lot as to

1) Whether the person had a mental illness
2) Which mental illness that person had

That makes it hard to see how heritable mental illness (or particular kinds of illness) are. One can only do linkage analysis with the diagnoses that people have been given...

It might be that the rates of mental illness have remained constant (or even that they have actually decreased) but now more people are presenting for help where they would have remained silent before.

The concept of mental illness has changed, however. It used to only be applied to people who needed to be confined (in asylums or by relatives) in order to stop them harming themselves or others. Nowdays it is certainly applied to people who are much much much less severe than that (though this isn't to undermine their suffering at all). It is just to say that once where we saw SPIRITUAL CRISIS or UNDERSTANDABLE RESPONSE TO UNFORTUNATE EVENTS we now see DEPRESSION and PROZAC and so on. 'Neurotic' cases (rather than 'psychotic') were originally treated by neurologists rather than psychiatrists. Middle class people who suffered from 'nerve complaints' were not thought to be suffering from mental illnesses. Whereas now, they are regarded as being psychiatric patients rather than neurological patitents. Or rather than as having a spiritual crisis.

The medicalization of (legitimate) distress / problems in living...

I see how it lines pockets. I don't really see how it helps...

Sometimes it is about the generalization power that different mechanisms have at different levels.

If one wants to explain why one particular member of a household developed anorexia rather than another particular member of a household then the explanation might look very different from when one asks:

Why is the prevalence of anorexia much much much higher in developed western nations than it is in developing nations?

Here one might attempt to appeal to genetic differences...

The trouble is that if you look at immigrants from developing to developed nations within two generations their prevalence looks the same.

What is left?

Why, the impact of skinny supermodels and cultural ideals, that is what. The appropriate explanation for it is going to be on the level of society.

Though in order to run a randomized double blind control trial on the effects of exposure to western ideals of beauty is something that can't be done for pragmatic / ethical reasons. And the pharma people go woo hoo! By making the randomized double blind control trial the 'epitome' of 'evidence based medicine' we have successfully biased things such that cultural mechanisms are effectively excluded from 'scientific' explanations! On with pharma ho!

You aren't going to find what the different cultures have genetically in common that raises the incidence of anorexia...
You probably aren't going to find what the different cultures have neurologically in common that raises the incidence of anorexia (the majority of the differences are caused by starvation rather than the cause of it)
But one doesn't need to reflect terribly much on differences in the ideal of beauty to see that we are getting SOME traction at least on an explanation.

Heritability of anorexia? Not sure that is a starter...
Unless, of course, you are looking at the heritability of a meme (cultural ideal).

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alexandra_k said:
> I was lost on your assumption that depressed people wouldn't have a chance to reproduce as much.

It isn't my assumption

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Sorry, Alex, Tracy's, not yours; I didn't make myself clear. The original post uses that assumption as an example.

It is "obvious" that both heredity and environment influence the course of people's mental health development. Could it be otherwise?

As for the influence of environment, can you say that the society in which we live is entirely benign in its influences on the mental health of its members?