Thinking positively: The genetics of high intelligence

Sibling similarity can reveal key insights into genetic architecture

The use of siblings to infer the factors influencing complex traits has been a cornerstone of quantitative genetics. Here, we utilise siblings for a novel application: the inference of genetic architecture, specifically that relating to individuals with extreme trait values (e.g. in the top 1%). Inferring the genetic architecture most relevant to this group of individuals is important because they are at the greatest risk of disease and may be more likely to harbour rare variants of large effect due to natural selection. We develop a theoretical framework that derives expected distributions of sibling trait values based on an index sibling's trait value, estimated trait heritability, and null assumptions that include infinitesimal genetic effects and environmental factors that are either controlled for or have combined Gaussian effects. This framework is then used to develop statistical tests powered to distinguish between trait tails characterised by common polygenic architecture from those that include substantial enrichments of de novo or rare variant (Mendelian) architecture. We apply our tests to UK Biobank data here, although we note that they can be used to infer genetic architecture in any cohort or health registry that includes siblings and their trait values, since these tests do not use genetic data. We describe how our approach has the potential to help disentangle the genetic and environmental causes of extreme trait values, and to improve the design and power of future sequencing studies to detect rare variants.

An economic model and evidence of the evolution of human intelligence in the Middle Pleistocene: Climate change and assortative mating

A main objective of this paper is to provide the first model of how climate change, working through sexual selection, could have led to dramatic increases in hominin brain size, and presumably intelligence, in the Middle Pleistocene. The model is built using core elements from the field of family economics, including assortative mating and specialization and complementarities between mates. The main assumptions are that family public goods (e.g., conversation, shelter, fire) were particularly cognitively intensive to produce and became increasingly important for child survival during glacial phases. Intermediate climates (e.g., not the depths of severe glacial phases) create the largest gains from specialization, encouraging negative assortative mating. In contrast, severe glacial phases encourage positive assortative mating because of the rising importance of family public goods. One testable hypothesis is that absence of severe glacial phases should have led to stasis in brain size. Two other testable hypotheses are that severe glacial phases should have led to speciation events, as well as increases in brain size. The evidence shows that there was a million-year stasis in cranial size prior to the start of the severe glacial phases. This stasis is broken by a speciation event (Homo heidelbergensis), with the oldest fossil evidence dated near the close of the first severe glacial phase. In the next 300 kyr, there are two additional severe glacial phases, accompanied by considerable increases in cranial capacity. The last speciation event is Homo sapiens, with the earliest fossils dated near the end of the last of these two glacial phases.

Interdisciplinary Approach to Biological and Health Implications in Selected Professional Competences

Everyday life’s hygiene and professional realities, especially in economically developed countries, indicate the need to modify the standards of pro-health programs as well as modern hygiene and work ergonomics programs. These observations are based on the problem of premature death caused by civilization diseases. The biological mechanisms associated with financial risk susceptibility are well described, but there is little data explaining the biological basis of neuroaccounting. Therefore, the aim of the study was to present relationships between personality traits, cognitive competences and biological factors shaping behavioral conditions in a multidisciplinary aspect. This critical review paper is an attempt to compile biological and psychological factors influencing the development of professional competences, especially decent in the area of accounting and finance. We analyzed existing literature from wide range of scientific disciplines (including economics, psychology, behavioral genetics) to create background to pursuit multidisciplinary research models in the field of neuroaccounting. This would help in pointing the best genetically based behavioral profile of future successful financial and accounting specialists.

Klerman's "credo" reconsidered: neo-Kraepelinianism, Spitzer's views, and what we can learn from the past

In 1978, G. Klerman published an essay in which he named the then-nascent "neo-Kraepelinian" movement and formulated a "credo" of nine propositions expressing the movement's essential claims and aspirations. Klerman's essay appeared on the eve of the triumph of neo-Kraepelinian ideas in the DSM-III. However, this diagnostic system has subsequently come under attack, opening the way for competing proposals for the future of psychiatric nosology. To better understand what is at stake, in this paper I provide a close reading and consideration of Klerman's credo in light of the past forty years of research and reflection. The credo is placed in the context of two equally seminal publications in the same year, one by S. Guze, the leading neo-Kraepelinian theorist, and the other by R. Spitzer and J. Endicott, defining mental disorder. The divergences between Spitzer and standard neo-Kraepelinianism are highlighted and argued to be much more important than is generally realized. The analysis of Klerman's credo is also argued to have implications for how to satisfactorily resolve the current nosological ferment in psychiatry. In addition to issues such as creating descriptive syndromal diagnostic criteria, overthrowing psychoanalytic dominance of psychiatry, and making psychiatry more scientific, neo-Kraepelinians were deeply concerned with the conceptual issue of the nature of mental disorder and the defense of psychiatry's medical legitimacy in response to antipsychiatric criticisms. These issues cannot be ignored, and I argue that proposals currently on offer to replace the neo-Kraepelinian system, especially popular proposals to replace it with dimensional measures, fail to adequately address them.

Estimating the Additive Heritability of Historiometric Eminence in a Super-Pedigree Comprised of Four Prominent Families

By merging analytical approaches from the fields of historiometrics and behavior genetics, a social pedigree-based estimate of the heritability of eminence is generated. Eminent individuals are identified using the Pantheon dataset. A single super-pedigree, comprised of four prominent and interrelated families (including the Wedgwood-Darwin, Arnold-Huxley, Keynes-Baha'u'lláh, and Benn-Rutherford pedigrees) is assembled, containing 30 eminent individuals out of 301 in total. Each eminent individual in the super-pedigree is assigned a relative measure of historical eminence (scaled from 1 to 100) with noneminent individuals assigned a score of 0. Utilizing a Bayesian pedigree-based heritability estimation procedure employing an informed prior, an additive heritability of eminence of .507 (95% CI [.434, .578]) was found. The finding that eminence is additively heritable is consistent with expectations from behavior-genetic studies of factors that are thought to underlie extraordinary accomplishment, which indicate that they are substantially additively heritable. Owing to the limited types of intermarriage present in the data, it was not possible to estimate the impact of nonadditive genetic contributions to heritability. Gene-by-environment interactions could not be estimated in the present analysis either; therefore, the finding that eminence is simply a function of additive genetic and nonshared environmental variance should be interpreted cautiously.

Super-Recognizers - a novel diagnostic framework, 70 cases, and guidelines for future work

When you hear the word Super-Recognizer, you may think of comic-book-hero-esque agents searching the underground to find people who went missing decades ago. Compared to this fantasy, the reality seems somewhat less exciting. Super-Recognizers (SRs) were initially reported a decade ago as a collateral while developing tests for developmental prosopagnosia. Today, the topic of SRs sparks interest from groups seeking to enhance scientific knowledge, public safety, or their monetary gain. With no immediate consequences of erroneous SR identification, there has been no pressure to establish a clear SR definition. This promotes heterogenous empirical evidence and the proliferation of unsupported claims in the media. Not only is this status quo unfortunate, it stands in opposition to the potential of special populations - both for science and application. SRs are a special population with imminent real-world value that can advance our understanding of brain functioning. To exploit their potential, I propose a needed formal framework for SR diagnosis, and introduce 70 cases identified based hereupon. These cases represent the core of a growing SR cohort, studied in my lab in the course of a long-term, multi-methodological research agenda involving academic and government collaborators. Finally, I provide recommendations for those interested in SR work, and highlight current caveats and future challenges.

How should we theorize about justice in the genomic era?

The sequencing of the human genome and advances in gene therapy and genomic editing, coupled with embryo selection techniques and a potential gerontological intervention, are some examples of the rapid technological advances of the "genetic revolution." This article addresses the methodological issue of how we should theorize about justice in the genomic era. Invoking the methodology of non-ideal theory, I argue that theorizing about justice in the genomic era entails theorizing about (1) the new inequalities that the genetic revolution could exacerbate (e.g., genetic discrimination, disability-related injustices, and gender inequality), and (2) those inequalities that the genetic revolution could help us mitigate (e.g., the risks of disease in early and late life). By doing so, normative theorists can ensure that we develop an account of justice that takes seriously not only individual rights, equality of opportunity, the cultural and sociopolitical aspects of disability, and equality between the sexes, but also the potential health benefits (to both individuals and populations) of attending to the evolutionary causes of morbidity and disability.

Maternal prenatal depressive symptoms and risk for early-life psychopathology in offspring: genetic analyses in the Norwegian Mother and Child Birth Cohort Study

BACKGROUND

Maternal prenatal depression is a known risk factor for early-life psychopathology among offspring; however, potential risk transmission mechanisms need to be distinguished. We aimed to test the relative importance of passive genetic transmission, direct exposure, and indirect exposure in the association between maternal prenatal depressive symptoms and early-life internalising and externalising psychopathology in offspring.

METHODS

We used structural equation modelling of phenotypic data and genetically informative relationships from the families of participants in the Norwegian Mother and Child Birth Cohort Study (MoBa). The analytic subsample of MoBa used in the current study comprises 22 195 mothers and 35 299 children. We used mothers' self-reported depressive symptoms during pregnancy, as captured by the Symptom Checklist, and their reports of symptoms of psychopathology in their offspring during the first few years of life (measured at 18, 36, and 60 months using the Child Behavior Checklist).

FINDINGS

Maternal prenatal depressive symptoms were found to be associated with early-life psychopathology primarily via intergenerationally shared genetic factors, which explained 41% (95% CI 36-46) of variance in children's internalising problems and 37% (30-44) of variance in children's externalising problems. For internalising problems, phenotypic transmission also contributed significantly, accounting for 14% (95% CI 5-19) of the association, but this contribution was found to be explained by exposure to concurrent maternal depressive symptoms, rather than by direct exposure in utero.

INTERPRETATION

Associations between maternal prenatal depressive symptoms and offspring behavioural outcomes in early childhood are likely to be at least partially explained by shared genes. This genetic confounding should be considered when attempting to quantify risks posed by in-utero exposure to maternal depressive symptoms.

FUNDING

UK Economic and Social Research Council, Norwegian Research Council, Norwegian Ministries of Health and Care Services, and Education & Research, Wellcome Trust, Royal Society, and National Institute for Health Research.

Assessing the evidence for shared genetic risks across psychiatric disorders and traits

Genetic influences play a significant role in risk for psychiatric disorders, prompting numerous endeavors to further understand their underlying genetic architecture. In this paper, we summarize and review evidence from traditional twin studies and more recent genome-wide molecular genetic analyses regarding two important issues that have proven particularly informative for psychiatric genetic research. First, emerging results are beginning to suggest that genetic risk factors for some (but not all) clinically diagnosed psychiatric disorders or extreme manifestations of psychiatric traits in the population share genetic risks with quantitative variation in milder traits of the same disorder throughout the general population. Second, there is now evidence for substantial sharing of genetic risks across different psychiatric disorders. This extends to the level of characteristic traits throughout the population, with which some clinical disorders also share genetic risks. In this review, we summarize and evaluate the evidence for these two issues, for a range of psychiatric disorders. We then critically appraise putative interpretations regarding the potential meaning of genetic correlation across psychiatric phenotypes. We highlight several new methods and studies which are already using these insights into the genetic architecture of psychiatric disorders to gain additional understanding regarding the underlying biology of these disorders. We conclude by outlining opportunities for future research in this area.

A neurocomputational model of developmental trajectories of gifted children under a polygenic model: When are gifted children held back by poor environments?

From the genetic side, giftedness in cognitive development is the result of contribution of many common genetic variants of small effect size, so called polygenicity (Spain et al., 2016). From the environmental side, educationalists have argued for the importance of the environment for sustaining early potential in children, showing that bright poor children are held back in their subsequent development (Feinstein, 2003a). Such correlational data need to be complemented by mechanistic models showing how gifted development results from the respective genetic and environmental influences. A neurocomputational model of cognitive development is presented, using artificial neural networks to simulate the development of a population of children. Variability was produced by many small differences in neurocomputational parameters each influenced by multiple artificial genes, instantiating a polygenic model, and by variations in the level of stimulation from the environment. The simulations captured several key empirical phenomena, including the non-linearity of developmental trajectories, asymmetries in the characteristics of the upper and lower tails of the population distribution, and the potential of poor environments to hold back bright children. At a computational level, 'gifted' networks tended to have higher capacity, higher plasticity, less noisy neural processing, a lower impact of regressive events, and a richer environment. However, individual instances presented heterogeneous contributions of these neurocomputational factors, suggesting giftedness has diverse causes.

A genome-wide association study for extremely high intelligence

We used a case-control genome-wide association (GWA) design with cases consisting of 1238 individuals from the top 0.0003 (~170 mean IQ) of the population distribution of intelligence and 8172 unselected population-based controls. The single-nucleotide polymorphism heritability for the extreme IQ trait was 0.33 (0.02), which is the highest so far for a cognitive phenotype, and significant genome-wide genetic correlations of 0.78 were observed with educational attainment and 0.86 with population IQ. Three variants in locus ADAM12 achieved genome-wide significance, although they did not replicate with published GWA analyses of normal-range IQ or educational attainment. A genome-wide polygenic score constructed from the GWA results accounted for 1.6% of the variance of intelligence in the normal range in an unselected sample of 3414 individuals, which is comparable to the variance explained by GWA studies of intelligence with substantially larger sample sizes. The gene family plexins, members of which are mutated in several monogenic neurodevelopmental disorders, was significantly enriched for associations with high IQ. This study shows the utility of extreme trait selection for genetic study of intelligence and suggests that extremely high intelligence is continuous genetically with normal-range intelligence in the population.

Fine mapping genetic associations between the HLA region and extremely high intelligence

General cognitive ability (intelligence) is one of the most heritable behavioural traits and most predictive of socially important outcomes and health. We hypothesized that some of the missing heritability of IQ might lie hidden in the human leukocyte antigen (HLA) region, which plays a critical role in many diseases and traits but is not well tagged in conventional GWAS. Using a uniquely powered design, we investigated whether fine-mapping of the HLA region could narrow the missing heritability gap. Our case-control design included 1,393 cases with extremely high intelligence scores (top 0.0003 of the population equivalent to IQ > 147) and 3,253 unselected population controls. We imputed variants in 200 genes across the HLA region, one SNP (rs444921) reached our criterion for study-wide significance. SNP-based heritability of the HLA variants was small and not significant (h2 = 0.3%, SE = 0.2%). A polygenic score from the case-control genetic association analysis of SNPs in the HLA region did not significantly predict individual differences in intelligence in an independent unselected sample. We conclude that although genetic variation in the HLA region is important to the aetiology of many disorders, it does not appear to be hiding much of the missing heritability of intelligence.

Cognitive ability and risk for substance misuse in men: genetic and environmental correlations in a longitudinal nation-wide family study

AIMS

To investigate the association in males between cognitive ability in late adolescence and subsequent substance misuse-related events, and to study the underlying genetic and environmental correlations.

DESIGN

A population-based longitudinal study with three different family-based designs. Cox proportional hazards models were conducted to investigate the association at the individual level. Bivariate quantitative genetic modelling in (1) full brothers and maternal half-brothers, (2) full brothers reared together and apart and (3) monozygotic and dizygotic twin brothers was used to estimate genetic and environmental correlations.

SETTING

Register-based study in Sweden.

PARTICIPANTS

The full sample included 1 402 333 Swedish men born 1958-91 and conscripted at mean age 18.2 [standard deviation (SD) = 0.5] years. A total of 1 361 066 men who had no substance misuse events before cognitive assessment at mandatory military conscription were included in the Cox regression models, with a follow-up time of up to 35.6 years.

MEASURES

Cognitive ability was assessed at conscription with the Swedish Enlistment Battery. Substance misuse events included alcohol- and drug-related court convictions, medical treatments and deaths, available from governmental registries.

FINDINGS

Lower cognitive ability in late adolescence predicted an increased risk for substance misuse events [hazard ratio (HR) for a 1-stanine unit decrease in cognitive ability: 1.29, 95% confidence interval (CI) = 1.29-1.30]. The association was somewhat attenuated within clusters of full brothers (HR = 1.21, 95% CI = 1.20-1.23). Quantitative genetic analyses indicated that the association was due primarily to genetic influences; the genetic correlations ranged between -0.39 (95% CI = -0.45, -0.34) and -0.52 (95% CI -0.55, -0.48) in the three different designs.

CONCLUSIONS

Shared genetic influences appear to underlie the association between low cognitive ability and subsequent risk for substance misuse events among Swedish men.

A genome-wide analysis of putative functional and exonic variation associated with extremely high intelligence

Although individual differences in intelligence (general cognitive ability) are highly heritable, molecular genetic analyses to date have had limited success in identifying specific loci responsible for its heritability. This study is the first to investigate exome variation in individuals of extremely high intelligence. Under the quantitative genetic model, sampling from the high extreme of the distribution should provide increased power to detect associations. We therefore performed a case-control association analysis with 1409 individuals drawn from the top 0.0003 (IQ >170) of the population distribution of intelligence and 3253 unselected population-based controls. Our analysis focused on putative functional exonic variants assayed on the Illumina HumanExome BeadChip. We did not observe any individual protein-altering variants that are reproducibly associated with extremely high intelligence and within the entire distribution of intelligence. Moreover, no significant associations were found for multiple rare alleles within individual genes. However, analyses using genome-wide similarity between unrelated individuals (genome-wide complex trait analysis) indicate that the genotyped functional protein-altering variation yields a heritability estimate of 17.4% (s.e. 1.7%) based on a liability model. In addition, investigation of nominally significant associations revealed fewer rare alleles associated with extremely high intelligence than would be expected under the null hypothesis. This observation is consistent with the hypothesis that rare functional alleles are more frequently detrimental than beneficial to intelligence.

Occupational attainment influences survival in autopsy-confirmed frontotemporal degeneration

OBJECTIVE

To examine the influence of occupational attainment and education on survival in autopsy-confirmed cases of frontotemporal lobar degeneration (FTLD) and Alzheimer disease (AD).

METHODS

We performed a retrospective chart review of 83 demographically matched, autopsy-confirmed FTLD (n = 34) and AD (n = 49) cases. Each patient's primary occupation was classified and ranked. Level of education was recorded in years. Survival was defined as time from symptom onset until death. Linear regression was used to test for associations among occupational attainment, education, and patient survival.

RESULTS

Median survival was 81 months for FTLD and 95 months for AD. Years of education and occupational attainment were similar for both groups. We found that higher occupational attainment was associated with longer survival in FTLD but not AD.

CONCLUSIONS

Our findings suggest that higher occupational attainment is associated with longer survival in autopsy-confirmed FTLD. The identification of protective factors associated with FTLD survival has important implications for estimates of prognosis and longitudinal studies such as treatment trials.