Developmental Cognitive Neuroepidemiology

In Superintelligence Bostrom writes:

'Our individual cognitive capacities can be strengthened in various ways, including by such traditional methods as education and training. Neurological development can be promoted by low-tech interventions such as optimizing maternal and infant nutrition, removing lead and other neurotoxic pollutants from the environment, eradicating parasites, ensuring adequate sleep and exercise, and preventing diseases that affect the brain. [...] 'According to the World Health Organization in 2007, nearly 2 billion individuals have insufficient iodine intake (The Lancet 2008). Severe iodine deficiency hinders neurological development and leads to cretinism, which involves an average loss of about 12.5 IQ points (Qian et al. 2005). The condition can be easily and inexpensively prevented though salt fortification (Horton et al. 2008).'^[1]

Summary

Here, I propose launching a new philanthropic cause area and academic field: 'Developmental Cognitive Neuroepidemiology' (DCN).

DCN combines the following two fields:

1. Neuroepidemiology, 'a branch of epidemiology involving the study of neurological disease and its determinants and frequency in human populations.' Put simply, Neuroepidemiology is the study of what causes brain disease and how many people are affected and how badly. For instance, alcoholism sometimes causes brain damage and reduced IQ; studying the causes of alcoholism, finding out how many alcoholics there are, how many of them have brain damage and how badly they are affected would be an example of neuroepidemiology. Another example is one paper that ~17 million IQ points have been lost due to exposure to pesticides.[5] 
2. (Human) Developmental cognitive neuroscience, is 'an interdisciplinary scientific field devoted to understanding psychological processes and their neurological bases in the developing human. It examines how the mind changes as children [and young adults] grow up, interrelations between that and how the brain is changing, and environmental and biological influences on the developing mind and brain.'

And so, in essence, DCN studies what causes brain disease—widely construed to also include suboptimal brain development and cognitive function—in children and young adults (eventually also across the whole life span), and how many are affected and how badly.

The field's aim might be to elevate optimal neurodevelopment to a similar rank on the policy agenda as physical development. I motivate this by examining the importance and scale of the problem. I focus on reviewing some previous work trying to quantify the scale of what might cause suboptimal cognitive development. I start by giving some concrete examples

Sometimes IQ loss during development is very cost-effective to prevent, e.g. preventing iodine deficiency ^[2],^[3] (supplementation or fortification of staple foods 100 additional years per $100 spent on supplements, and an increase in ~1k-2k IQ points (7-10 IQ points for ~185 children). This ~100 IQ points per ~$1 spent. Each point increase in IQ test scores raises income by ~$100-$1000 per year after holding a variety of factors constant and so benefit-cost ratios of select interventions might be very high. Increasing IQ from current mean (100) to the top 2 percent of society (130) increases wages by ~$10k,^[4] and so raising the IQ of 100M people would to such an extent would raise world GDP by at least $1T.

Importance / Scale

Intelligence and healthy cognitive neurodevelopment is an important prerequisite for a flourishing life and suboptimal neurodevelopment might also have high social costs.

For instance, Caplan argues that education raises support for capitalism, free markets, globalization, civil liberties and tolerance, and reduces racism and sexism. Correcting for intelligence cuts education's impact by ~1/3.^[5]

As a result of suboptimal child neurodevelopment we likely lessen the effectiveness of education for hundreds of millions or even billions—I review the evidence below. In contrast, early childhood education has mixed evidence.^[6] However, we spend a lot of money on early childhood education, but very little on cognitive development. This might be because education is much less controversial and that the idea that intelligence is fixed to a substantial extent in early childhood or in utero is uncomfortable and controversial (as it might be conflated with genetic differences in intelligence between cultures).

Suboptimal child neurodevelopment might have drastic general equilibrium effects as well. People with low IQs might not be able to understand and answer conditional hypothetical questions ^[7] (e.g. ''How would you have felt yesterday evening if you hadn't eaten breakfast or lunch?' 'What do you mean? I did eat breakfast and lunch.' 'Yes, but if you had not, how would you have felt?' 'Why are you saying that I didn't eat breakfast? I just told you that did.' 'Imagine that you hadn't eaten it, though. How would you have felt?' 'I don't understand the question.').

Specific Examples of some potentially highly cost-effective public health problems that cause suboptimal neurodevelopment

Consider the literature on the 'fetal origins hypothesis' and child development, where early environment affects cognitive development and later life outcomes.^[8] Some of the effect sizes are downright incredible (not using this term lightly) and its implications might be 'big, if true' and so deserve further study.

Iodine deficiency

For example, salt iodization is cheap and might improve (population-level) cognitive development and IQ. ^[9],^[10] In India, children in iodine-poor districts who were exposed to a decrease in iodine-fortified salt in early life that was almost random, are '1-8 percentage points less likely to be able to do any math or reading'.^[11]

In China, females in the rural areas with a 1SD reduction in goiter rates (a proxy for iodine deficiency) have a ~15% increase in cognitive ability. Females who benefit from the new salt also obtain 0.5 additional years of schooling and have a higher educational attainment.^[12]

There are other natural experiments that show an even more dramatic effect of salt iodization in the past,^[13] up to an increase of 15 IQ points. In contrast, while there are some RCTs that suggest that improving iodine deficiency in children improves cognitive functions (summarized in a meta-analysis^[14]), the evidence is not as clear-cut as sample sizes in RCTs are much lower, participants were not followed over their whole development and it is deemed unethical to deprive people of micronutrients they need.

Even in 2019, ~5m newborns will be affected by full-blown iodine deficiency disorders.^[15] However this underestimates the economic deficit resulting from suboptimal iodine intake.

Iodine deficiency affects 780M people globally. Even in rich countries there might be substantial deficiency.^[16]

Figure: Iodine nutrition based on the median urinary iodine concentration, by country. Figure adapted from Zimmermann et al. ^[17]

Other micronutrient deficiencies

Other micronutrient deficiencies are also still widespread:

Global Distribution and Disease Burden Related to Micronutrient Deficiencies in 2011^[18]

Iron deficiency might affect school enrollment.^[19]

IQ might also be affected by acute and transient micronutrient deficiencies, and so multivitamin & iodine supplementation might raise IQ.^[20]

There are many other problems that can improve neurodevelopment.

Lead poisoning

Lead poisoning is harming the cognitive ability and educational opportunities of hundreds of millions of children: Lead poisoning is affecting children 800M children globally—that's around 1 in 3—have levels of lead in their blood at or above the level that requires intervention. Most of these children live in Africa and Asia.^[21]

Leaded fuel reduced the IQ of everyone born before 1990 by ~4.25%. Millennials are the first to be born with unleaded gas.^[22]

Environmental lead levels from leaded gasoline are still around in cities today, and cause continued neurotoxicity.^[23]

Figure. Children's average blood lead levels by country (μg/dL) source 

The Toxic Truth, UNICEF: 'Lead is more dangerous for children than it is for adults. Children absorb it more readily and they drink more water relative to their body weight than adults do. It particularly affects children's developing brains and has long-term effects, including deficits in cognitive ability, lower educational attainment, behavioral disorders, increased tendencies for violent crime, and reduced lifetime earnings. A pooled analysis of lead exposure and intellectual function found that children with higher (30 μg/dL) blood lead levels had IQ levels of almost seven points less than children with lower (2.4 μg/dL) blood lead levels. And evidence from the US found that high blood lead levels before the age of six are strongly associated with poor academic achievement in primary school grades.'

Since lead poisoning affects children in poor countries most, and since lead poisoning is detrimental to children's educational achievement, perhaps the education sector should invest more in research to understand the long-term educational effects on exposure to lead and in cross-sector efforts to prevent and control exposure to lead.

Infectious disease prevalence

National average IQ and parasite stress correlates strongly r ≈-0.8 (p<0.0001).^[24] 

Infectious disease exposure is associated with neurocognitive function in humans and one study finds that an index aggregating exposure to several infectious diseases like toxoplasmosis was associated with neurocognitive function.^[25]

COVID-19: Cognitive deficits in people who have recovered from Covid

For instance, there's some disagreement around how much (long) Covid affects cognition, but generally, the cognitive decline following acute viral infections and strong evidence for smell distortions post Covid, suggest that Covid affects the brain and thus might plausibly affect cognition. One study finds 0.04 SD IQ difference between people without respiratory symptoms (on the order of ~1 IQ point). Given that there are many millions of infections the IQ loss might be substantial.

Evidence review: existing reviews on this topic

Other reviews on this topic find the following interventions:

1. One review found that pollution, nutrition, disease, weather, smoking, alcohol etc.^[26] can affect neurodevelopment.

The following paper lists predictors of IQs and which has some interesting models / figures:

Predictors of IQ

Biodeterminist's Guide to Parenting, by Scott Alexander of Slate Star Codex:

E.g. 'Study after study shows higher intelligence (2-4 points), more favorable personality traits (for example, 33% less extreme shyness) and greater height (0.6 cm) in winter/spring babies (1, 2, 3, 4).'

'Below are all the interventions considered, my probability that the effect is real, and the number of IQ points gained. 'Probability it works' is my totally made up wild guess as to how likely it is to be a real causal effect. 'Probability it applies' is my totally made up wild guess as to how likely it is an average reader can benefit from it. For example, licorice has a low probability of application, because you probably weren't planning to eat a ton of licorice anyway. Some things have partial probabilities of application; you may get a little benefit from changing your location if you had been planning on living in California, but not the full benefit you would get if you had been planning on living in Mississippi.

The best case scenario — in which every single study I cited was the gospel truth, someone reading this had been planning to do everything wrong, and now they are planning to do everything right — nets us an extra 90 IQ points, meaning that it would be enough to bring an average IQ 100 child (which of course the child who did everything wrong would not have been) to an IQ 190 child, which is around the level historians speculate Isaac Netwon could've been at.'

The Health-Education Link

From: The Health-Education Link | Hauke Hillebrandt and Hayden Wilkinson

Figure: Impact on years of schooling per US$100 spent for various interventions, based on available evidence. Partly adapted from J-PAL.^[53] Note that some of these estimates are based on only one paper and should be taken as indications rather than exact measures. However, though inexact, there are orders of magnitude differences between the different interventions

From: Endocrine-disrupting chemicals: implications for human health

Table. Exposure–outcome associations with a probability of evidence for causation identified up to 2015

Further reading

• Prenatal exposure to airborne polycyclic aromatic hydrocarbons and IQ: estimated benefit of pollution reduction.
• Air pollution
• Estimating Burden and Disease Costs of Exposure to Endocrine-Disrupting Chemicals in the EU

Neglectedness, Tractability concerns

There might be stark cross-cultural differences in IQ due to suboptimal neurodevelopment caused by poverty that could be too politically touchy to discuss, despite it being intuitive that, say, early childhood nutrition might affect intelligence on a population level. This makes the cause quite neglected. However, crucially, DCN does not look at genetic differences in cognition—rather it only examines environmental and thus malleable causes.

On the flip side, childhood development seems to be a pretty popular area of philanthropy and so there is already a lot of money going into it.

Candidate Grants

Given that this literature around 'fetal origins hypothesis' has been around for so long and people still don't talk about it much, maybe the best thing a philanthropist could do might be to go a bit 'for the throat of the problem' and go more meta by:

• Raise awareness around the literature by having the scientists popularize the research e.g. in a popular science book
• At scale: For value of information: Fund general research, institutes, conferences on the fetal origins hypothesis and optimal (childhood) development more generally, what factors affect it and by how much, prevalence and what we can do about it

Shovel ready grantees might be:

• Fund Noam Angrist who invented LAYS to come up with a similar measure for neurodevelopment
• Youssef Oulhote^[54] and David C. Bellinger- who mention 'Neuroepidemiology' in a paper.^[55] 
• Bellinger is 'known for his research on the neurotoxic effects of exposure to certain chemicals in children, as well as the effects of medical conditions that develop early in life on children. One of his studies, published in 2012, concluded that ~17m IQ points have been lost due to exposure to pesticides.'^[56]
• OR Authors of this paper to set this up:

• Janet Currie
• Research- Valentina Duque
• Douglas Almond | Columbia | Economics 

'The Global Burden Of Suboptimal Neurodevelopment Study'

The Gates foundation has funded two interesting projects on epidemiology- that could inspire analogous projects in DCN:

1. The Global Burden of Disease study,^[57] which aims to map the entirety of human disease- see Global Burden of Disease (GBD) study visualization tool here:

Global Burden of Disease study visualization tool

However, while the Global Burden of Disease does include neurological diseases that are developmental, like Autism and tries to quantify the disease burden with methodologies like the disability-adjusted life year (DALY), this might not capture many cases of suboptimal mental development and many relevant social costs. And so while we have 'global burden of disease study', we do not yet have a 'Global Burden of suboptimal intelligence study'. This study measures how many IQ points are lost due to various causes and risk factors, just like the Global Burden of Disease study at the Institute for Health Metrics (See visualization here).

For instance, a child who through poor nutrition in childhood has their IQ reduced from 140 to 125, and thus still being normal functioning, perhaps even have a higher self-reported well-being, but this is not captured by the GBD.

A philanthropist could fund scientists to try to comprehensively map the Global Burden of suboptimal neurodevelopment from the biological to the social (more below).

'Suboptimal Neurodevelopment Priorities Project'

In a second step, the Gates Foundation funded the Disease Control Priorities Project (DCP) (which inspired Toby Ord's seminal EA paper The Moral Imperative toward Cost-Effectiveness in Global Health).^[58] The DCP tried to find estimate the cost-effectiveness of different global health interventions with measures like $ per DALY averted and then rank them by their cost-effectiveness.

Analogously, one fund a Neurodevelopmental Priorities Project that aims to find what interventions are most cost-effective to improve intelligence/ cognition i.e. how many IQ points per $. It might look at different global mental interventions to prevent say IQ loss (e.g. reducing lead and pesticide exposure, improving infant nutrition, micronutrient fortification, etc.), and then see how much it would cost to implement the interventions to arrive at a cost-effectiveness metric such as $ per IQ point loss averted. In addition to finding high benefit-cost ratios, one might also look use the GBD-equivalent suggested earlier to where the highest benefit minus cost can be found and the efficient of the two are (e.g. relatively cost-effective interventions i.e. high benefit-cost ratios in terms of say $ per IQ point loss averted that can scale to avert billions of lost IQ points). Crucially, DCN must not necessarily be about IQ, but could be about other cognitive dysfunction that is on the normal spectrum and has social costs or creates harm. One might imagine suboptimal neural development that increases depression or anxiety.

'Robustly good' philanthropic interventions in DCN

• Continue to fund robustly good charities recommended by Givewell which improve developmental outcomes
• Fund more Charity Entrepreneurship's Lead Exposure Elimination Project
• Create super-salt fortified w/ iron, iodine, and folic acid:

• See Can Double Fortification of Salt with Iron and Iodine Reduce Anemia, Iron Deficiency Anemia, Iron Deficiency, Iodine Deficiency, and Functional Outcomes? Evidence of Efficacy, Effectiveness, and Safety
• And double fortification of salt with folic acid

• Fund scientists to create the best Baby Formula and open source it

Beyond biological causes

Eventually, the field might only look at 'biological causes' but also examine how intelligence and executive functioning is reduced by:

1. Distracting technology, which might reduce IQ.^[59]
2. Poverty, which reduces IQ.^[60]
3. Lacking money or time can lead one to make poorer decisions, possibly because poverty imposes a cognitive load that saps attention and reduces effort.
4. Childhood adversity ^[61]
5. The Cognitive Dimension of Household Labor
6. High CO2 concentration indoors
7. Ill mental health like depression
8. Etc.—that's why it might actually warrant a whole new field

Eventually it could also construe 'development' more widely and look at IQ loss across the lifespan (according to famous neuroscientist Eric Kandel something a double digit percentage of all adults over 65 experience 'mild cognitive decline' something that is not dementia but might not be captured by the GBD, but could potentially even helped by therapeutics like nootropics, but is currently not deemed treatable.

Consider for inspiration this figure of a model of from 'The Mental Wealth of Nations' model:^[62]

Establishing the field of Developmental Cognitive Neuroepidemiology might help with human flourishing across the lifespan.

Further reading

• The fluoride wars rage on 
• Lead exposure in childhood linked to lower IQ, lower status jobs, as adults: Leaded gasoline creates a natural experiment in long-term study
• Strong evidence for the continued contribution of lead deposited during the 20th century to the atmospheric environment in London of today | PNAS 
• Childhood Lead Exposure and Adult Outcomes | Child Development
• Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial

References