Saturday, January 31, 2009

Science Spending and Justice

Political philosophers champion many different distributive principles that provide us with a benchmark for measuring the justness of the policies of government. For example, we may ask what the government is going to do to help redress inequality in our society, be it socio-economic and/or cultural inequality. Indeed these concerns are arguably the dominant concerns of liberal egalitarians.

I myself am actually very sympathetic to the sensibilities underlying liberal egalitarianism; however, I believe that the principles often championed by philosophers (like Rawls's difference principle or luck egalitarianism) actually skew our understanding of what really constitutes justice and good government. This is so because we tend to take what I call the "narrow view" of justice. This view is narrow in two senses. Firstly, it focuses on a very small list of things that actually matter to people's well being (namely $$); secondly, it is narrow in that it looks at the short-term rather than long-term picture of things.

Furthermore, the egalitarian instincts that philosophers appeal to actually reflect sensibilities that evolved from the immediate-return nomadic hunter societies we historically lived in but do not inhabit anymore (I will post more about this at a future time). And thus today, in large, complex, and highly developed societies these instincts are actually a form of cognitive bias that impair our ability to make reasonable judgements concerning what constitutes a fair distribution of the different benefits of social cooperation.

The central aspiration of decent government, according to this narrow vision of justice, is to pursue policies that will transfer particular goods (i.e. wealth and income) from some (i.e. the "haves") and give them to others (i.e. the "have nots"). Now one danger with this exclusive focus on re-distributing wealth is that it can lead us to ignore other issues, issues that also raise fundamental concerns of justice. Case in point-- what should the government's stance be on science? (e.g. how much to fund basic science?).

I have raised this concern many times before (see here). And in the past week it appears that Canada and the United States are going in two opposite directions in this respect. This story in the Globe this week notes that the Conservative government's budget cut the budget of Genome Canada, a non-profit non-governmental funding organization that finances large-scale science in Canada, from $140 million to $0 {though from this info from Genome Canada itself suggests that this might not be an accurate story of the current state of funding}. Contrast that negative story with what is happening in the United States. According to this "News of the Week" piece in Science, "academic researchers are on the verge of receiving a major influx of federal funding as part of a 2-year, $825 billion economic stimulus package moving rapidly through Congress".

To appreciate why justice requires an investment in science one has to have a nuanced public ethic that goes beyond the simplistic assumptions of "narrow justice". The word “science” comes from the Latin scientia, which means “having knowledge”. Knowledge is humanity’s greatest tool for improving the quality of life we can expect to enjoy on this planet (indeed this was something that Marx appreciated, hence why I think his account of human history is one worth taking seriously).

What will an investment in science likely bring? How about greater wealth and better health. Of course the critic might claim that creating more wealth and health is itself not the real goal; rather, what really matters is ensuring that these benefits are "fairly distributed". Well, much depends on the time-frame one adopts (in terms of measuring how fair the distribution is) as well as an appreciation of the interconnection between these different benefits. These points are addressed in my latest (though admittedly unconventional!) paper here.

Society is not a zero sum game, and realizing that is essential if we are to transcend the instincts that have been selected for when things really were a zero sum game (e.g. when food was gathered daily for rapid consumption). And so our evolutionary history is part of the reason why we continue to neglect the relation between justice and science policy. We have evolved to deal with what Dawkin's calls "middle world"-- and historically this was a world where we existed in small communities and had to decide how to share the rewards of the "immediate return" economy. But such sensibilities leave us ill-prepared for grappling with the question of justice in delayed-return conditions. And that is why science policy tends to be ignored by egalitarian philosophers (and almost everyone else).


Thursday, January 29, 2009

PNAS Study Finds CR Benefits Memory

Monday I posted this, noting the exciting advances being made with sirtuin activating compounds (which mimic calorie restriction) that could decelerate human aging, thus delaying all the afflictions that currently ravage most humans in their 60's, 70's, and 80's.

Now sceptics typically raise the following two concerns (amongst others)-- (1) we still do not know what the impact of calorie restriction is on humans (in terms of health and longevity benefits) and (2) keeping the body healthy as we age is only of limited value if our minds are not also kept healthy. Well, this study published this week in the Proceedings of the National Academy of Science should help ease both of these sceptical worries. The study found that calorie restriction actually improves the memory of elderly humans. This provides yet further reason for us to get behind the science that could lead to a safe and effective pharmaceutical intervention that mimics the effects of calorie restriction! Here is the abstract:

Animal studies suggest that diets low in calories and rich in unsaturated fatty acids (UFA) are beneficial for cognitive function in age. Here, we tested in a prospective interventional design whether the same effects can be induced in humans. Fifty healthy, normal- to overweight elderly subjects (29 females, mean age 60.5 years, mean body mass index 28 kg/m2) were stratified into 3 groups: (i) caloric restriction (30% reduction), (ii) relative increased intake of UFAs (20% increase, unchanged total fat), and (iii) control. Before and after 3 months of intervention, memory performance was assessed under standardized conditions. We found a significant increase in verbal memory scores after caloric restriction (mean increase 20%; P < 0.001), which was correlated with decreases in fasting plasma levels of insulin and high sensitive C-reactive protein, most pronounced in subjects with best adherence to the diet (all r values < −0.8; all P values <0.05). Levels of brain-derived neurotrophic factor remained unchanged. No significant memory changes were observed in the other 2 groups. This interventional trial demonstrates beneficial effects of caloric restriction on memory performance in healthy elderly subjects. Mechanisms underlying this improvement might include higher synaptic plasticity and stimulation of neurofacilitatory pathways in the brain because of improved insulin sensitivity and reduced inflammatory activity. Our study may help to generate novel prevention strategies to maintain cognitive functions into old age.

Studies like this raise so many fascinating issues. Contrast, for example, these findings with the ones I noted earlier-- that postnatal poverty affects the brain development of children. Now everyone is going to want to prevent the adverse impact poverty has on the brain development of children. But what about the adverse impact these same people could be vulnerable to later in life? Should we not also want to benefit their cognitive capacities at *all* ages, not just early in life? And should we not seek to mitigate the internal vulnerabilities of our biology rather than just those external environmental factors that can harm our cognitive capacities? Once we overcome "ageism" and the shortsightedness of worrying exclusively about external threats to our health prospects (rather than the evolutionary causes of the diseases of aging) we will be better positioned to take a truly inclusive approach to improving the health prospects of the world's populations this century.


Tuesday, January 27, 2009

Blogs and Reading Groups

There are two interesting reading groups going on in the blogosphere at the moment. Over a Crooked Timber they are tackling G.A. Cohen's new book Rescuing Justice and Equality; and at Jacob Levy's blog they are reading Nancy Rosenblum's On the Side of Angels.

If I had more time I would contribute to these but I am swamped at the moment. I read a draft of Cohen's book already and have lots to say about it. So I hope to write up some detailed responses to his book in the near future (with a title along the lines of "Rescuing Justice from Idealization and Abstraction").


Monday, January 26, 2009

60 Minutes Report on Anti-Aging Pill

The wealth and prosperity of a nation is only as strong as its citizens are healthy. The history of humanity is a history of civilizations ravaged by diseases of one kind or another; diseases that took the lives of loved ones prematurely and robbed society of productive individuals who could have helped generate more knowledge and wealth.

Whether it be the "Black Plague", small pox, malaria, cancer or heart disease, human populations are susceptible to a diverse array of chronic and infectious diseases that threaten both the lives of individuals and the prosperity of nations. And so it is imperative that we think rationally about how we can best respond to these diverse threats to our health and survival. We need accurate data concerning the probable risks of disease facing the world's populations this century and an open mind about the potential strategies for dealing with these threats.

The greatest threat facing the world's existing 6.7+ billion population are the chronic diseases associated with aging. In the year 2005, approximately 55 million people died. Of that number, 35 million died of chronic disease. That number is twice the number of deaths due to infectious diseases (including HIV/AIDS, tuberculosis and malaria), maternal and perinatal conditions, and nutritional deficiencies combined. 35 million deaths a year dwarf the estimated deaths caused by climate change-- approximately 150 000 deaths.

So the current rate of cellular and molecular damage caused by aging kills approximately 230% more humans than the temperature rises experienced since the 1970's. Furthermore, the death toll of aging will continue to outstrip that associated with climate change given that the world's populations continue to age, with a projected 2 billion people expected to reach the age of 60 in 2050. Furthermore, numerous experiments have been conducted on various organisms that demonstrate the aging can be decelerated. So the science of modifying the biology of aging is much, much further ahead than the science of modifying the global temperature (indeed there is no science of the latter). And this is a good thing as the benefits of the former will far surpass the benefits of the latter (and only cost a fraction of the latter).

Given all this, one might expect governments to be showering scientists with huge grants to tackle aging, and that researchers would be eager to cut across traditional disciplinary boundaries to help make the discipline of applied gerontology a reality. And you might also think that there would be a booming "grass roots" movement among the general population championing the importance of utilizing science to help aging populations enjoy more health. Sadly, none of this is the case.

If we really want to significantly improve the health prospects of the majority of humans alive today, and if we really want to help prevent the most prevalent diseases of the 21st century, and if we really want to invest in the economy of the future then we must get behind aging research.

Last night 60 Minutes aired this excellent video on the advances being made with resveratrol and similar sirtuin activating compounds.


Saturday, January 24, 2009

Stem Cell–Derived Therapy Approved for Clinical Trial

Back in 1990 the first human somatic gene therapy trial began (see this). The subjects of the earliest gene therapy experiments were children who suffered from a rare genetic disease called adenosine deaminase deficiency (ADA), a form of SCID (also known as the " bubble boy" disease-- see here).

Today, 19 years later, there are over 1400 clinical trials for gene therapy worldwide (see here) for a variety of diseases ranging from cancer, single gene disorders, infectious diseases and neurological disorders. Most of these clinical trials are in the first phase, which means they have yet to be shown to be safe and effective therapeutic interventions. But there is hope, as this story and this story indicate. And there has also been serious setbacks.

It is against the background of the noble aspirations and yet complex challenges facing gene therapy that I think we should embrace the good news that the first embryonic stem cell derived therapy has been approved for clinical trial.

Contrary to what the media reports, the real story here is not that that these stem cells are derived from human embryos and that this raises profound questions about the ethics of improving the life of some at the cost of others-- for these are not embryos that anyone intends to implant in a uterus and (possibly) grow into a human. The real story is how dogma and ignorance (and politics!) threatens to hold science and medicine back, and thus delay therapeutic benefits to people who have suffered spinal cord injuries (and countless other possible diseases).

So this announcement is an important move forward for medical science. But we should appreciate the complex challenges that lay ahead, and adopt a realistic standard for measuring the success of these novel interventions. One that measures things in terms of decades rather than a year or two.


Saturday, January 17, 2009

Aging, Chronic Disease and the "Black Plague"

Blogging has been light the past few weeks as I have been preparing two different talks on aging and aging research that I am giving this coming week.

The first talk will be tomorrow afternoon to Quill here in Kingston. Quill stands for "Queen's Institute for Lifelong Learning". I am really looking forward to getting feedback on this talk which is entitled "Slowing Human Aging: Ethical and Social Issues".

The main message of my talk is that there is both good news and bad news. And one has to be cautious concerning how one frames both of these things. The bad news, in terms of the projected number of human deaths caused by chronic disease (like heart disease, cancer, stroke, AD, etc.), is really bad. Indeed, chronic disease will cause an unprecedented number of deaths this century. This is due to two things: (1) there are more people in the world now than there ever has been before and (2) the world's populations are living to older ages, which makes them more vulnerable to heart disease, cancer, stroke, AD, etc.

So in conveying the current situation one wants to be accurate, and not merely "hype" the cause one is championing (which is something people often do with respect to other important problems, like climate change). OK, so here are the facts:

In the year 2005, approximately 55 million people died. Of that number, 35 million died of chronic disease. That number is twice the number of deaths due to infectious diseases (including HIV/AIDS, tuberculosis and malaria), maternal and perinatal conditions, and nutritional deficiencies. That is a staggering figure. Furthermore, between the years 2005-2015 WHO estimates that 220 million people will die from chronic disease, most of them (144 million deaths) in lower middle income countries like China and India. The diseases associated with aging are not, contrary to popular perception, only a problem for people living in the developed world. Indeed, being vulnerable to disability and frailty is a much greater disadvantage if one lives in a poor society with no decent health care or pension, as the link between income and "ability to work" is much more direct. So the chronic diseases associated with aging are a problem for all societies, not only the richest countries in the world.

One last point to make to illustrate the magnitude of the problem of chronic disease. It is estimated that between the mid-14th century and mid-17th century, the "Black Death" plague killed approximately 25 million people. This means that the current deaths caused by chronic disease in just one year outnumber the deaths caused by 3 centuries of the "Black Death" plague. This clearly illustrates why the imperative to combat chronic disease is one of the greatest imperatives ever facing humanity. And since aging is the major cause of these afflictions, one of the greatest moral imperatives facing humanity today is to tackle aging itself so that we can avoid the unprecedented rise in chronic disease that is expected to befall the world's populations this century.

OK, enough about the bad news. Now for the good news (this is abbreviated as I am pressed for time at the moment). Despite the herculean task facing us-- trying to prevent all the numerous diseases and afflictions that come with aging-- the good news is we don't have to find a cure for every single disease of aging in order to make serious headway in terms of extending our opportunity for health. The shortcut is to modify the rate of aging itself. This is not as outlandish as many might believe it to be. This video, for example, shows how far along the science really is. So does this and this.

What do we need to do?
(1) increase public funding for basic research on the biology of aging.
(2) shift our focus away from the exclusive focus on the proximate causes of disease to the ultimate (or evolutionary) cause of disease.
(3) encourage the kind of interdisciplinary research that will bring together epidemiologists, biodemographers, evolutionary biologists, doctors, etc. to better understand the role aging plays in the development of disease and the possible ways of promoting "healthy aging".
(4) dispel the public's misperception that retarding aging would be a bad thing (e.g. because it would destroy the earth or simply extend the length of time we live as frail) rather than one of the most important things humanity could achieve.

And finally (5) get the public behind evolution rather than holding onto the outdated ideas of our intellectually naive past. We also need to educate people to distinguish between the real science of aging research and quacks who are more than happy to sell products that have not been tested for safety and/or efficacy. And we need to educate people about the risks of aging, and the things they could do themselves *right now* to reduce their risks of morbidity and mortality (like these things).

IF we can decelerate the rate of molecular and cellular damage caused by aging, this would mean that the next generation would experience more healthy years. Nursing homes might become extinct. It would reduce strains on the health care system and society and individuals would reap enormous economic benefits. And these would be benefits that benefit all future generations. And I believe that that is a future worth fighting for!!


Thursday, January 15, 2009

Sleep, Colds and the Costs of Insomnia

Those following this blog will know I have an interest in sleep (see here). Some might think this is a bizarre interest to have. But I don't think it is when one considers the fact that we spend approximately 1/3 of our lives sleeping. Why do we sleep? And how do our sleeping habits impact our health (for better or worse)? I think these are fascinating questions.

I came across two new sleep studies to add to my growing collection. Do you feel tired? Do you have a cold? Well this study in the Archives of Internal Medicine suggests that it is possible that sleep plays a causal role in cold susceptibility.

And what, you might also wonder, are the economic burdens of insomnia? The latest issue of the journal Sleep has this study which finds:

The total annual cost of insomnia in the province of Quebec was estimated at $6.6 billion (Cdn$). This includes direct costs associated with insomnia-motivated health-care consultations ($191.2 million) and transportation for these consultations ($36.6 million), prescription medications ($16.5 million), over the-counter products ($1.8 million) and alcohol used as a sleep aid ($339.8 million). Annual indirect costs associated with insomnia-related absenteeism were estimated at $970.6 million, with insomnia-related productivity losses estimated at $5.0 billion. The average annual per-person costs (direct and indirect combined) were $5,010 for individuals with insomnia syndrome, $1,431 for individuals presenting with symptoms, and $421 for good sleepers.

This study suggests that the economic burden of insomnia is very high, with the largest proportion of all expenses (76%) attributable to insomnia-related work absences and reduced productivity. As the economic burden of untreated insomnia is much higher than that of treating insomnia, future clinical trials should evaluate the cost-benefits, cost-utility, and cost-effectiveness of insomnia therapies.


Main Menu (Jan 2009)

Wednesday, January 14, 2009

Men's Preference for Financial Risk and Women's Preference for Masculine Faces and Intelligence

Following on from the theme of my previous post...evolutionary biology offers incredible new insights into our understanding not only of health and disease, but also human behavior.

The current and previous issues of the journal Evolution and Human Behavior have many great examples of this. I want to highlight just three. Consider first this article, which examines the role of testosterone in male risk preferences. Here is a sample:

The findings of this study suggest an association between activational effects of testosterone and, possibly, its organizational effects during puberty and behaviors related to risktaking in men. Men with higher levels of circulating testosterone and masculine faces are more likely to make risky financial decisions.

....Monetary transactions are a recent phenomenon in human history, but the acquisition and accumulation of resources by men is not. Money is, in this sense, a proximal currency used to maximize returns in some other currency, such as utility or fitness (Daly & Wilson, 2002). Men may have evolved to engage in riskier behaviors compared to women because the potential returns in terms of fitness payoffs can be higher. A woman's reproductive success is limited by the number of offspring she can produce whereas in men it is limited by the number of partners he can attract. Increased resources in men may translate into both increased mating opportunities and increased child survivorship. Indeed, studies have found that women find wealth to be an attractive quality when choosing a mate and value it more than men do in potential mates. Therefore, there may have been increased selection pressure on men to maximize resource acquisition in order to attract members of the opposite sex.

We suggest that one possible way for a man to increase his resources relative to other men would be to engage in risky financial investments with the possibility of lucrative monetary returns. Since men differ in the degree to which they are willing to trade off expected value against variance, they will also differ in their resulting financial payoffs.

Having greater financial payoffs can result in greater access to resources and, thus, greater ability to attract women. Potentially, financial risk-taking might be comparable to other risky male behaviors associated with reproduction. For example, males of many species engage in direct male–male competition over both resources and mates, and this behavior is often activated by testosterone during the breeding season (Balthazart, 1983; Harding, 1981). In light of financial risk being a potential form of male–male competition, there are clear reasons to expect that men with higher levels of circulating testosterone would be more economically risky as evidenced by our study.

And the current issue of the journal has this piece which examines why women prefer masculine faces. Here is the abstract:

Women's preference for masculine faces varies with hormonal state, sociosexuality, and relationship status, but the underlying mechanisms are poorly understood. We hypothesized that hormones and psychosexual factors (sociosexuality, sexual inhibition/excitation) mediate the perception and evaluation of male faces thereby influencing women's preferences. We used functional magnetic resonance imaging to measure brain activity in 12 women as they evaluated pictures of male faces (half 30% masculinized, half 30% feminized). Participants were heterosexual women, age 23–28 years, who were not in a committed relationship and not using hormonal contraception. Women were tested during both the follicular and luteal phase of their menstrual cycle. We found five brain regions related to face and risk processing that responded more to the masculinized than to the feminized faces, including the superior temporal gyrus, precentral gyrus, posterior cingulate cortex, inferior parietal lobule, and anterior cingulate cortex. Increased activation in the anterior cingulate cortex, specifically, may indicate that women perceive masculinized faces to be both more risky and more attractive. We did not see any areas that were more strongly activated by feminized faces. Levels of activation were influenced by hormonal and psychosexual factors. The patterns of hormonally and psychosexually mediated neural activation observed may offer insight into the cognitive processes underlying women's partner preferences.

But those men that do not possess masculine faces need not despair! For this article suggests that intelligence and creativity also play a big factor in mate appeal.


Wednesday, January 07, 2009

Looking for Love? Trying Looking in Our Brain and Genes

Imagine this. You are single and sign up with an online dating agency to help you find your "perfect mate". Within a few days a match is found. And the good news is that the person you have been matched to has scored very high on a genetic test for being predisposed to quality romantic relationships! Sound like science fiction? It is, but it may not be long before something like this is a reailty.

The latest issue of Nature has this fascinating article on the neural and genetic components of love. Here is a sample:

... researchers are attempting to isolate and identify the neural and genetic components underlying this seemingly uniquely human emotion. Indeed, biologists may soon be able to reduce certain mental states associated with love to a biochemical chain of events. This has implications for the evolution of human sexuality, and raises important societal issues given our increasing use of genetic tests to screen for certain behaviours, and of drugs to modulate mental processes.

Animal models have greatly aided our understanding of the mechanisms that regulate emotions — particularly for evolutionarily conserved states such as fear and anxiety. These advances have led to pharmaceutical therapies for anxiety, phobias and post-traumatic stress disorders. Such models are also beginning to shed light on love.

We are not alone in being able to form intense and enduring social ties. Take the mother–infant bond. Whether or not the emotional connection between a ewe and her lamb, or a female macaque and her offspring, is qualitatively similar to human motherly love, it is highly likely that these relationships share evolutionarily conserved brain mechanisms. In humans, rats and sheep, the hormone oxytocin is released during labour, delivery and nursing. In ewes, an infusion of oxytocin into the brain results in rapid bonding with a foreign lamb.

....Similarly, in humans, different forms of the AVPR1A gene are associated with variation in pair bonding and relationship quality. A recent study shows that men with a particular AVPR1A variant are twice as likely as men without it to remain unmarried, or when married, twice as likely to report a recent crisis in their marriage. Spouses of men with the variant also express more dissatisfaction in their relationships than do those of men lacking it. For both voles and humans, AVPR1A genetic polymorphisms predict how much vasopressin receptor is expressed in the brain.

The BBC has the scoop on this story here. This research raises many interesting issues to consider, especially for me given that love is the foundation of my perfectionist account of ethics. So much to ponder, so little time!


Nature's "15 Evolutionary Gems"

The journal Nature have made freely available this list of 15 evolutionary gems. . Here is the list:

Gems from the fossil record
1 Land-living ancestors of whales
2 From water to land
3 The origin of feathers
4 The evolutionary history of teeth
5 The origin of the vertebrate skeleton

Gems from habitats
6 Natural selection in speciation
7 Natural selection in lizards
8 A case of co-evolution
9 Differential dispersal in wild birds
10 Selective survival in wild guppies
11 Evolutionary history matters

Gems from molecular processes
12 Darwin’s Galapagos finches
13 Microevolution meets macroevolution
14 Toxin resistance in snakes and clams
15 Variation versus stability

The gems demonstrate the explanatory power of the principle of natural selection.


Tuesday, January 06, 2009

Sociology and Genetics

Might we be in the midst of a "genetic turn" in sociology?

This interesting piece in The Chronicle of Higher Education notes the concerns sociologists have in integrating the findings of the biological sciences into their analyses. The piece also highlights this special issue of the American Journal of Sociology which is a special issue on genetics. Here is a sample from the editorial of that issue:

This special issue was motivated by what appeared to be a strange paradox.Just about every week the Science Times—one of the places where science meets the public—enthusiastically reported on new research findings that revealed the genetic basis for something (intelligence, voting behavior, obesity, depression, sexual behavior, religiosity, orgasms, altruism and egoism, generosity, thrift, and, of course, earwax type). Aside from the earwax, the phenomena reported to be “genetic” were largely of sociological interest. Yet sociologists were rarely discussed in these articles. Meanwhile, the prevailing sentiment of the discipline appeared to be that the emphasis on genetic expression as explanation for human behavior and social outcomes was at best undermining sociological perspectives
and at worst a return of the eugenicist project of the first half of the 20th century. The two reactions—enthusiastic embrace and uncritical adoption (as represented in the Science Times) and fear and loathing (from sociologists)— appeared to be in some tension. However, thinking about it a little more, one realizes that they arise from the same source: a naive overvaluation of “genetics.”

And here are some of the abstracts from the issue:

Happiness and Success: Genes, Families, and the Psychological Effects of Socioeconomic Position and Social Support
By Jason Schnittker

Although there is considerable evidence linking success—including wealth, marriage, and friendships—to happiness, this relationship might not reflect, as is often assumed, the effects of the proximate environment on well-being. Such an interpretation is contravened by evidence that both happiness and the environment are influenced by genetic factors and family upbringing. Using the National Survey of Midlife Development in the United States, which includes a subsample of twins, this study evaluates the relationship between happiness and various features of success before and after eliminating the influence of endowments. The results suggest that many putative indicators of the environment are highly heritable and, indeed, that the same genes that affect the environment may affect happiness as well. Yet the results also suggest that the role of genetic endowments varies considerably across different features of success, suggesting complex patterns of selection, reinforcement, and causation among genes and the environment.

The Intergenerational Correlation in Weight: How Genetic Resemblance Reveals the Social Role of Families
By Molly A. Martin

According to behavioral genetics research, the intergenerational correlation in weight derives solely from shared genetic predispositions, but complete genetic determinism contradicts the scientific consensus that social and behavioral change underlies the modern obesity epidemic. To address this conundrum, this article utilizes sibling data from the National Longitudinal Study of Adolescent Health and extends structural equation sibling models to incorporate siblings' genetic relationships in order to explore the role of families' social characteristics for adolescent weight. The article is the first to demonstrate that the association between parents' obesity and adolescent weight is both social and genetic. Furthermore, by incorporating genetic information, the shared and social origins of the correlation between inactivity and weight are better revealed.

Environmental Contingencies and Genetic Propensities: Social Capital, Educational Continuation, and Dopamine Receptor Gene DRD21

By Michael J. Shanahan, Stephen Vaisey, Lance D. Erickson, Andrew Smolen

Studies of gene-environment interplay typically focus on one environmental factor at a time, resulting in a constrained view of social context. The concept of environmental contingency is introduced as a corrective. Drawing on the National Longitudinal Study of Adolescent Health and qualitative comparative analysis, the authors focus on an example involving social capital, a gene associated with a dopamine receptor (DRD2), and educational continuation beyond secondary school. For boys, (1) DRD2 risk is associated with a decreased likelihood of school continuation; (2) one configuration of social capital—high parental socioeconomic status, high parental involvement in school, and a high-quality school—compensates for this negative relationship, consistent with environmental contingency; but (3) boys with DRD2 risk are less commonly observed in settings that are rich in social capital.