One of the most intriguing recent papers seeking to document the notion that genes and cultures co-evolve comes from Chiao & Blizinsky (2010) of Northwestern University.
Tracking A Gene that Predictably Leads to Increased Depression & Anxiety In Western Societies
One of their starting points is arguably the most studied mental health gene, the serotonin transporter functional polymorphism , 5-HTTLPR, (Canli & Lesch, 2007; Caspi et al, 2003; Lesch et al, 1996; Pezawas et al., 2005; Risch et al, 2009; Sen, Burmeister & Ghosh, 2004; Taylor et al, 2006; Uher & McGuffin, 2008).
Conventional wisdom derived from the abundant scientific and clinical literature has long held that persons have the short form of 5-HTTLPR, have a distinctly higher chance of developing mood disorders, particularly major depression and anxiety, particularly if triggered by stressful life events. Those with the long form of 5-HTTLPR seem to enjoy a measure of protection, despite adversities in their life histories (Fox, Ridgewell & Ashwin, 2009).
The World Wide Reported Frequency of Depression & Anxiety Disorders
Chiao & Blizinsky note however, that the statistical prevalence of diagnoses for depression and anxiety disorders varies across nations and cultures. For example, certain Asian nations, most notably Taiwan, South Korea, and especially the People’s Republic of China, report markedly lower rates, while the US , UK, and Australia report among the highest rates.(Weissman et al, 1996)
Does this mean that people are deliriously happy in the Peoples Republic and consistently sad in the US? The answer to this is clearly No, but there must be something to account for this consistently reported difference.
Does this mean that there are many more psychiatrists in the US, UK and Australia who will diagnose mood disorders and write SSRI prescriptions? The answer to this is yes, although Chiao & Blizinsky factor this out. (They do report that there may be more cultural stigma in seeking treatment for depression and anxiety in East Asian countries, but also note that countries like Mexico and Brazil also have a lower rate of diagnosis and treatment of mood disorders, despite the fact Brazilians and Mexicans are not notably ethnically or politically related to these East Asian groups, have greater access to psychiatrists, and not any particularly well documented social disapproval of seeking some form of help for situationally induced emotional distress.)
Chiao & Blizinsky also account for variations in Gross Domestic Product, per-capita earnings, and a number of other factors that would be expected to sway incidence of depression and anxiety. In terms of wealth measurements, the US, UK and Australia do quite well (even in this economic recession we would still do relatively well against most other nations), and certainly would not be predisposed to a higher frequency of mood disorders in need of SSRIs if this was driven primarily by chronic economic want.
Furthermore, there is quite a disparity in per-capita wealth between the Asian people of the Peoples Republic of China on one hand and Asians in South Korea and Taiwan on the other, with the latter two significantly wealthier by most measures. Yet, the low rate reported for diagnosis and treatment of mood disorders is essentially the same across all three counties.
The World Wide Distribution of the Short Form of 5-HTTLPR Favoring Depression/Anxiety
Chiao & Blizinsky then hypothesized that this disparity in depression and anxiety must be a case where more Americans, Brits, and Aussies, must have the short form of the 5-HTTLPR.
But almost exactly the opposite is the case. East Asian nations with very low reported rates of depression and anxiety have among the very highest frequencies of the short form of 5-HTTLPR within their population.
Ordinarily, this would cause the overthrow of the well established linkage of the short form of 5-HTTLPR with increased propensity for adverse mood disorders, but not even Chiao and Blizinsky believe that to be necessary.
Why Then Don’t East Asians with Short Form 5-HTTLPR Develop Depression & Anxiety As Often?
Chiao & Blizinsky argue that at least historically, if not currently, cultures evolved in Asia with the kind of structure that buffered the genetic propensity for mental reactions in people who would ordinarily become notably depressed and anxious over adverse “triggering” life events and circumstances.
They note that what bound these Asian cultures together in the past was a strong emphasis on economic order and social harmony. At least historically, if not currently, deprivation was a common experience, and losses were shared across the population.
The idea of casting out depressed or anxious people with the notion that it would greatly improve communal circumstances, seemed alien concepts for such a long period of time in historic East Asia that people with the short form of 5-HTTLPR were able to reproduce and perpetuate this gene to an extraordinary degree, because it did not come with social or economic consequences that caused them to die out in East Asia (Gintis, 2004).
But critically, “blaming behaviors” for failure in these cultures tended not to fall on individuals who had become depressed or anxious, but rather on a lack of well-coordinated collective effort or on the mandate of Heaven. Indeed, individuals in East Asian cultures in the past have historically “construed” their sense of self-worth largely in relation to what they could help their village or extended clan accomplish rather than what they could accomplish on their own. And, if nothing was accomplished, then it was a matter beyond the control of the village or the clan, and particularly, not their fault as an individual .
In East Asia, a culture of communal fatalism, in these regards seemed the most sensible, because the range of an individual’s choice of occupations, and the degree to which one’s economic or social lot could be improved, were much more narrowly circumscribed than in western cultures.
Any individuals in historic East Asian cultures who consistently expressed outspoken optimism and tried to persuade the community to hope for substantially better returns by creatively making fundamental changes in the social or economic order were likely taken as being mental ill in these societies in historic times.
In fact, people lacking in optimism and personal initiative -----people who would be regarded as depressed and anxious people in western societies -----might very well have fit right in with a fatalistic culture.
If Historic Asian Cultures Did Not Evolutionarily Discriminate Against Those with the Short Form of 5-HTTLPR, Did This Form Offer Evolutionary Advantages Within Those Cultures?
It has been proposed that one way that the brains of individuals with the short form of 5-HTTLPR malfunction is with heightened sensitivity of their amygdalas (Hariri et al, 2002; Munafo, Brown & Hariri, 2008; Pezawas et al, 2005 ).
The amygdala is that portion of the brain that adds emotional emphasis that not only concentrates one’s thoughts on important tasks and memories in an effort to prioritize them, but is absolutely essential for danger avoidance.
One measure in which depressed and anxious persons, particularly those with the short form of 5-HTTLPR excel in an adverse sort of way, is their ability to operate in a self-protective fashion via a state of hypervigilance in terms of their amygdala function. (Osinsinsky et al, 2008). Their amygdalas seems to “fire” sooner, “fire” more often, and “fire” to a greater degree. Their amygdalas seem to signal danger everywhere (Beevers et al, 2007).
In western cultures, this hypervigilance is seen as making the affected person appear afraid of everything, and would be expected to contribute to his or her sense of hopelessness. In particular, it would make the person disinclined to try out things that would help them break out of their adverse mood.
In western cultures, such individuals might be seen by others, and eventually see themselves, as self-defeating pessimists or even cowards. The social or economic disadvantages they have, or the failures they experience, might well be attributed to flaws in their character, such as lack of initiative or courage.
In evolutionary terms in western cultures, such individuals are not likely to thrive and reproduce in large enough numbers to pass on their genes to a large proportion of subsequent generations, because hypervigilant behaviors that stifle self-improvement and economic advancement are socially unattractive, and put them at a disadvantage against optimistic, creative individuals who are valued more highly in western societies.
In other words, in western societies, these would be the very people who would be strongly advised “to get help” including consulting psychiatrists who would diagnose and treat their depression and anxiety so as to improve their function in society. This “be treated or be ashamed of oneself, ” culture , of course, might well explain the higher reported rates of diagnosis in western cultures for those syndromes, despite the reduced rate of the short form of the 5-HTTLPR gene.
But Chiao & Blizinsky note that a highly active amygdala, spurred by inheritance of the short form of 5-HTTLPR, confers advantages in historically highly conformist groups. It served as an early warning system to register signs of disapproval, particularly in the facial expressions of members of their in-group.
This might well explain that while people across cultures recognize the general emotional nature of facial expressions (anger, happiness, disgust, sadness, etc. ), they differ greatly in their sensitivity to the depth of the emotions, and nuances within expressions, when dealing with people from outside their culture.
This may be particularly true of westerners encountering Asian cultures.
In other words, a westerner who is completely fluent in Mandarin might well address an audience in Beijing, and even understand that the tersely worded polite verbal feedback is insincere. That foreign speaker could even sense that the listeners were in fact angry, but cannot gauge as well as Chinese members of the same audience, just how angry the members of the audience are, or whether or not the faces in the audience were expressing a mix of emotions.
Gauging when a person is right to be afraid is particularly important to reproductive success in authoritarian regimes that historically held sway in East Asia. An inability in those cultures in those times, to determine that one was in trouble was likely to get a person incarcerated or worse, definitely limiting their chances to pass on any genes.
Where Does the Notion of Protection Against Infectious Diseases Come Into This Story of the Variance in Effect of a Gene Between Differing Cultures & Nations?
Randy Thornhill at the University of New Mexico has assembled a team of evolutionary biologists and evolutionary psychologists who have developed a model for the evolution of cultures based on how epidemics of microbes and parasites adversely influenced them, and on the measures those cultures took to defend themselves. In their analysis (See Fincher et al, 2008) those societies that were repeatedly hit by infestations responded by collectivist, protectionist measures, where the free will and “out-of-line” behavior of nonconformist members was seen as a danger to the entire group. Xenophobia that encouraged quarantine and authoritarianism to enforce hygiene (as much as was understood in those era, at any rate) worked to limit the impact of these infectious disease disasters, and by extension according to Chiao & Blizinsky, individuals whose genetic makeup inclined them to conform and closely identify with groupthink, were vastly more likely to live long enough to be able to pass on those genes, than we freethinking western-types, it would appear.
It is not hard to see now that the same short form of 5- HTTLPR genes can make for a differing way of viewing one’s success and sense of worth. The short form can actually promote the construal of oneself as an obedient contributor to the health and wealth of the commune in Eastern cultures, while in Western ones it leads people to see themselves as, at best, failed initiators of actions that determine one’s individual achievement and status, and thereby determine their self-worth.
Tony Stankus, FSLA, tstankus@uark.edu Life Sciences Librarian, Science Coordinator, & Professor
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