Genetic correlation

Interpretation

Genetic correlations are not the same as heritability, as it is about the overlap between the two sets of influences and not their absolute magnitude; two traits could be both highly heritable but not be genetically correlated or have small heritabilities and be completely correlated (as long as the heritabilities are non-zero).

For example, consider two traits - dark skin and black hair. These two traits may individually have a very high heritability (most of the population-level variation in the trait due to genetic differences, or in simpler terms, genetics contributes significantly to these two traits), however, they may still have a very low genetic correlation if, for instance, these two traits were being controlled by different, non-overlapping, non-linked genetic loci.

A genetic correlation between two traits will tend to produce phenotypic correlations - eg the genetic correlation between intelligence and SES or education and family SES implies that intelligence/SES will also correlate phenotypically. The phenotypic correlation will be limited by the degree of genetic correlation and also by the heritability of each trait. The expected phenotypic correlation is the bivariate heritability' and can be calculated as the square roots of the heritabilities multiplied by the genetic correlation. (Using a Plomin example, for two traits with heritabilities of 0.60 & 0.23, r g = 0.75 , and phenotypic correlation of r=0.45 the bivariate heritability would be 0.60 ⋅ 0.75 ⋅ 0.23 = 0.28 , so of the observed phenotypic correlation, 0.28/0.45 = 62% of it is due to genetics.)

Cause

Genetic correlations can arise due to:

1. linkage disequilibrium (two neighboring genes tend to be inherited together, each affecting a different trait)
2. biological pleiotropy (a single gene having multiple otherwise unrelated biological effects)
3. mediated pleiotropy (a gene causes trait X and trait X causes trait Y).
4. biases: population stratification such as ancestry or assortative mating (sometimes called "gametic phase disequilibrium"), spurious stratification such as ascertainment bias/self-selection or Berkson's paradox, or misclassification of diagnoses

Causes of changes in traits

Genetic correlations are scientifically useful because genetic correlations can be analyzed over time within an individual longitudinally (eg intelligence is stable over a lifetime, due to the same genetic influences - childhood genetically correlates r g = 0.62 with old age), or across studies or populations or ethnic groups/races, or across diagnoses, allowing discovery of whether different genes influence a trait over a lifetime (typically, they do not), whether different genes influence a trait in different populations due to differing local environments, whether there is disease heterogeneity across times or places or sex (particularly in psychiatric diagnoses there is uncertainty whether 1 country's 'autism' or 'schizophrenia' is the same as another's or whether diagnostic categories have shifted over time/place leading to different levels of ascertainment bias), and to what degree traits like autoimmune or psychiatric disorders or cognitive functioning meaningfully cluster due sharing a biological basis and genetic architecture (for example, reading & mathematics disability genetically correlate, consistent with the Generalist Genes Hypothesis, and these genetic correlations explain the observed phenotypic correlations or 'co-morbidity'; IQ and specific measures of cognitive performance such as verbal, spatial, and memory tasks, reaction time, long-term memory, executive function etc all show high genetic correlations as do neuroanatomical measurements, and the correlations may increase with age, with implications for the etiology & nature of intelligence). This can be an important constraint on conceptualizations of the two traits: traits which seem different phenotypically but which share a common genetic basis require an explanation for how these genes can influence both traits.

Boosting GWASes

Genetic correlations can be used in GWASes by using polygenic scores or genome-wide hits for one (often more easily measured) trait to increase the prior probability of variants for a second trait; for example, since intelligence and years of education are highly genetically correlated, a GWAS for education will inherently also be a GWAS for intelligence and be able to predict variance in intelligence as well and the strongest SNP candidates can be used to increase the statistical power of a smaller GWAS, or one could do a GWAS for multiple traits jointly. Genetic correlations can also quantify the contribution of correlations <1 across datasets which might create a false "missing heritability", by estimating the extent to which differing measurement methods, racial influences, or environments create only partially overlapping sets of relevant genetic variants.

Breeding

Hairless dogs have imperfect teeth; long-haired and coarse-haired animals are apt to have, as is asserted, long or many horns; pigeons with feathered feet have skin between their outer toes; pigeons with short beaks have small feet, and those with long beaks large feet. Hence if man goes on selecting, and thus augmenting any peculiarity, he will almost certainly modify unintentionally other parts of the structure, owing to the mysterious laws of correlation.

Genetic correlations are also useful in applied contexts such as plant/animal breeding by allowing substitution of more easily measured but highly genetically correlated characteristics (particularly in the case of sex-linked or binary traits under the liability-threshold model, where differences in the phenotype can rarely be observed but another highly correlated measure, perhaps an endophenotype, is available in all individuals), compensating for different environments than the breeding was carried out in, making more accurate predictions of breeding value using the multivariate breeder's equation as compared to predictions based on the univariate breeder's equation using only per-trait heritability & assuming independence of traits, and avoiding unexpected consequences by taking into consideration that artificial selection for/against trait X will also increase/decrease all traits which positively/negatively correlate with X.

Breeding experiments on genetically correlated traits can measure the extent to which correlated traits are inherently developmentally linked & response is constrained, and which can be dissociated. Some traits, such as the size of eye spots on the butterfly Bicyclus anynana can be dissociated in breeding, but other pairs, such as eye spot colors, have resisted efforts.

Computing the genetic correlation

Genetic correlations require a genetically informative sample. They can be estimated by using breeding experiments on two traits of known heritability and selecting on one trait to measure the change in the other trait (allowing inferring the genetic correlation), family/adoption/twin studies (analyzed using SEMs or DeFries-Fulker extremes analysis), molecular estimation of relatedness such as GCTA, methods employing polygenic scores like LD score regression, BOLT-REML, CPBayes, or HESS, comparison of genome-wide SNP hits in GWASes (as a loose lower bound), and phenotypic correlations of populations with at least some related individuals. (As with estimating SNP heritability, the better computational scaling & the ability to estimate only using public polygenic scores is a particular advantage for LD score regression over competing methods, and combined with the increasing availability of polygenic scores from datasets like the UK Biobank has led to an explosion of genetic correlation research in the 2010s.) The methods are related to Haseman-Elston regression & PCGC regression. Such methods are typically genome-wide, but it is also possible to estimate genetic correlations for specific variants or genome regions.

One way to consider it is using trait X in twin 1 to predict trait Y in twin 2 for monozygotic and dizygotic twins (ie using twin 1's IQ to predict twin 2's brain volume); if this cross-correlation is larger for the more genetically-similar monozygotic twins than for the dizygotic twins, the similarity indicates that the traits are not genetically independent and there is some common genetics influencing both IQ and brain volume. (Statistical power can be boosted by using siblings as well.)

Genetic correlations are affected by methodological concerns; underestimation of heritability, such as due to assortative mating, will lead to overestimates of longitudinal genetic correlation, and moderate levels of misdiagnoses can create pseudo correlations. As they are affected by heritabilities of both traits, genetic correlations have low statistical power, especially in the presence of measurement errors biasing heritability downwards, because "estimates of genetic correlations are usually subject to rather large sampling errors and therefore seldom very precise": the standard error of an estimate r g is σ ( r g ) = 1 − r g 2 2 ⋅ σ ( h x 2 ) ⋅ σ ( h y 2 ) h x 2 ⋅ h y 2 . (Larger genetic correlations & heritabilities will be estimated more precisely.) However, inclusion of genetic correlations in an analysis of a pleiotropic trait can boost power for the same reason that multivariate regressions are more powerful than separate univariate regressions.

Twin methods have the advantage of being usable without detailed biological data, with human genetic correlations calculated as far back as the 1970s and animal/plant genetic correlations calculated in the 1930s, and require sample sizes in the hundreds for being well-powered, but they have the disadvantage of making assumptions which have been criticized, and in the case of rare traits like anorexia nervosa it may be difficult to find enough twins with a diagnosis to make meaningful cross-twin comparisons, and can only be estimated with access to the twin data; molecular genetic methods like GCTA or LD score regression have the advantage of not requiring specific degrees of relatedness and so can easily study rare traits using case-control designs, which also reduces the number of assumptions they rely on, but those methods could not be run until recently, require large sample sizes in the thousands or hundreds of thousands (to obtain precise SNP heritability estimates, see the standard error formula), may require individual-level genetic data (in the case of GCTA but not LD score regression)

Given a genetic covariance matrix, the genetic correlation is computed by standardizing this, i.e., by converting the covariance matrix to a correlation matrix. For example, if two traits, say height and weight have the following additive genetic variance-covariance matrix:

Then the genetic correlation is .55, as seen is the standardized matrix below:

In practice, structural equation modeling applications such as Mx or OpenMx (and before that, historically, LISREL) are used to calculate both the genetic covariance matrix and its standardized form. In R, cov2cor() will standardize the matrix.

Typically, published reports will provide genetic variance components that have been standardized as a proportion of total variance (for instance in an ACE twin study model standardised as a proportion of V-total = A+C+E). In this case, the metric for computing the genetic covariance (the variance within the genetic covariance matrix) is lost (because of the standardizing process), so you cannot readily estimate the genetic correlation of two traits from such published models. Multivariate models (such as the Cholesky decomposition) will, however, allow the viewer to see shared genetic effects (as opposed to the genetic correlation) by following path rules. It is important therefore to provide the unstandardised path coefficients in publications.

Human correlations

Genetic correlations, positive & negative, have been measured for a wide variety of human traits using primarily twin and molecular genetic methods.

Anthropometric

facial averageness/attractiveness

baldness

tiredness/forced expiratory volume

tiredness/grip strength

tiredness/self-rated health

tiredness/longevity

self-reported health/longevity

life satisfaction/positive affect

exercise/longevity

self-reported health/forced expiratory volume in one second (FEV1)

tiredness/obesity

tiredness/BMI

baseline BMI/increase in BMI

chronotype/BMI

undersleeping/BMI

oversleeping/BMI

morning chronotype/BMI

difficulty sleeping/BMI

difficulty sleeping/waist circumference

difficulty sleeping/waist-hip ratio

difficulty sleeping/neck bone mineral density

daytime sleepiness/BMI

daytime sleepiness/self-reported sleep duration

daytime sleepiness/difficulty sleeping

daytime sleepiness/waist circumference

daytime sleepiness/waist-hip ratio

sex/sleep pattern

sex/sleep quality

self-reported sleep duration/birth weight

self-reported sleep duration/difficulty sleeping

self-reported sleep duration/neck bone mineral density

difficulty sleeping/birth weight

breast size/BMI

sweet taste perception/BMI

tiredness/waist-hip ratio

self-reported health/BMI

early puberty/BMI

age at first sex/BMI

exercise/BMI

exercise/waist circumference

body fat percentage/cardiorespiratory fitness (VO2max)

BMI/waist circumference

waist-hip ratio/BMI

fasting insulin/BMI

fasting glucose/waist-hip ratio

heart rate recovery/vagal rebound

longevity/resting heart rate

exercise/resting heart rate

exercise/heart rate recovery

exercise/respiratory sinus arrhythmia

ambulatory heart period/respiratory sinus arrhythmia

respiration rate/respiratory sinus arrhythmia

weight/height

spousal height

birth weight//infant head circumference

birth weight/birth length

birth weight/childhood height

birth weight/adult height

birth weight/waist circumference

birth weight/hip circumference

birth weight/BMI

spousal BMI

birth weight/childhood obesity

birth weight/adult obesity

birth weight/pubertal growth

age at first sex/height

age at first sex/birth weight

age at first sex/birth length

early puberty/age at first sex

early puberty/age at first birth

age at first sex/age at first birth

age at first sex/age at menarche

age at first sex/age at voice breaking

age at first sex/age at menopause

age at first sex/number of sexual partners

age at first sex/number of children ever born

age at first sex/childless

age at first sex/happiness

age at first birth/age at menarche

age at first birth/age at menopause

age at first birth/voice breaking

age at first birth/polycystic ovary syndrome

age at first birth/age at first sexual intercourse

age at first birth/birth weight

age at first birth/years of education

age at first birth/cigarettes per day

age at first birth/ever smoked

age at first birth/age onset of smoking

age at first birth/triglycerides

age at first birth/type 2 diabetes

age at first birth/fasting insulin level

age at first birth/waist-hip ratio

spousal waist-to-hip ratio

age at first birth/BMI

age at first birth/height

number of children ever born (fertility)/age at first sexual intercourse

number of children ever born/years of education

number of children ever born/number of grandchildren ever born

anthropometric measurements made on the 6 major sub-populations of the Solomon Islands (Harvard Solomon Islands Project)

weight

sitting height

height

biacromial diameter

bicristal diameter (biiliac breadth)

chest breadth

foot length

total facial height

upper facial height

nose length

nose breadth

bicondylar humerus diameter

wrist breadth

hand breadth

hand length

bicondylar femur diameter

foot breadth

head length

head breadth

minimum frontal diameter

bizygomatic diameter

bigonial diameter

head circumference

upper arm circumference

calf circumference

triceps skinfold thickness

subscapular skinfold thickness

intracranial volume/height

intracranial volume/child head circumference

intracranial volume/birth length

intracranial volume/birth weight

birth length/intelligence

birth weight/intelligence

head motion/BMI

head motion/waist circumference

head motion/hypertension

head motion/monetary delay temporal discounting

Neuroanatomical

correlations between left/right hemisphere volume, volumes/thicknesses of individual regions, white matter connectivity, correlation between volume/thickness and cognitive performance on WM/IQ tests etc, stability of brain regions over time due to stable genetics (see also brain size and intelligence)

epigenetic age acceleration/diffuse plaque

epigenetic age acceleration/neuritic plaque

epigenetic age acceleration/working memory

brain atrophy/blood pulse pressure

subcortical abnormal white matter/ependymal white matter

abnormal white matter/systolic blood pressure

Eyes Test empathy score/volume of the caudate nucleus

Eyes Test empathy score/volume of the putamen

head motion/default mode network connectivity

Intelligence

intelligence longitudinal stability and consistency

cognitive performance & neuroanatomical properties

behavioral/emotional problems in children

intelligence/reading

intelligence/longevity

tiredness/verbal-numerical reasoning

self-reported health/intelligence

age at first sex/intelligence

intelligence/Openness

intelligence/Conscientiousness

intelligence/Neuroticism

intelligence/anxiety

intelligence/socioeconomic status (SES)

intelligence/verbal-numerical reasoning/processing speed/short-term memory/Trail Making test

spatial reasoning

Coronary artery disease/verbal-numerical reasoning

Stroke: ischaemic/verbal-numerical reasoning

Stroke: cardioembolic/verbal-numerical reasoning

Stroke: large vessel disease/verbal-numerical reasoning

Stroke: small vessel disease/verbal-numerical reasoning

Type 2 diabetes/verbal-numerical reasoning

ADHD/verbal-numerical reasoning

ADHD/intelligence

Alzheimer's disease/verbal-numerical reasoning

Autism/verbal-numerical reasoning

autism/intelligence

Bipolar disorder/verbal-numerical reasoning

Major depressive disorder/verbal-numerical reasoning

schizophrenia/intelligence

Schizophrenia/verbal-numerical reasoning

Schizophrenia/memory

Schizophrenia/reaction time

Schizophrenia/educational attainment

intelligence/temperament

Hippocampal volume/verbal-numerical reasoning

Intracranial volume (ICV)/verbal-numerical reasoning

intracranial volume/childhood cognitive function

intracranial volume/adult cognitive function

Infant head circumference/verbal-numerical reasoning

Infant head circumference/intelligence

Blood pressure: diastolic/verbal-numerical reasoning

Blood pressure: systolic/verbal-numerical reasoning

BMI/verbal-numerical reasoning

intelligence/weight

Height/verbal-numerical reasoning

intelligence/height

Longevity/verbal-numerical reasoning

Forced expiratory volume in 1 s (FEV1)/verbal-numerical reasoning

Childhood cognitive ability/verbal-numerical reasoning

Coronary artery disease/reaction time

Stroke: ischaemic/reaction time

Stroke: cardioembolic/reaction time

Stroke: large vessel disease/reaction time

Stroke: small vessel disease/reaction time

Type 2 diabetes/reaction time

ADHD/reaction time

Alzheimer's disease/reaction time

Autism/reaction time

Bipolar disorder/reaction time

Major depressive disorder/reaction time

Hippocampal volume/reaction time

Intracranial volume/reaction time

Infant head circumference/reaction time

Blood pressure: diastolic/reaction time

Blood pressure: systolic/reaction time

BMI/reaction time

Height/reaction time

Longevity/reaction time

Forced expiratory volume in 1 s (FEV1)/reaction time

Childhood cognitive ability/reaction time

Coronary artery disease/memory

Stroke: ischaemic/memory

Stroke: cardioembolic/memory

Stroke: large vessel disease/memory

Stroke: small vessel disease/memory

Type 2 diabetes/memory

ADHD/memory

Alzheimer's disease/memory

Autism/memory

Bipolar disorder/memory

Major depressive disorder/memory

Hippocampal volume/memory

Intracranial volume/memory

Infant head circumference/memory

Blood pressure: diastolic/memory

Blood pressure: systolic/memory

BMI/memory

Height/memory

Longevity/memory

Forced expiratory volume in 1 s (FEV1)/memory

Childhood cognitive ability/memory

go-no-go/fast task reaction time

intelligence/reaction-time variability

intelligence/reaction-time

reaction-time variability/ADHD

reaction-time/reaction-time variability

frequency of talking or texting on smartphone/intelligence

Education

education longitudinal stability

education/intelligence

college degree/intelligence

Years of education/verbal-numerical reasoning

Years of education/reaction time

Years of education/memory

Hippocampal volume/educational attainment

Intracranial volume/educational attainment

Infant head circumference/educational attainment

Childhood cognitive ability/educational attainment

College degree/memory

College degree/reaction time

College degree/verbal-numerical reasoning

intelligence/GCSE scores

education/family SES

spousal education

education/SES

education/wealth

education/income

education/welfare

education/credit scores

education/social mobility

education/working overseas

education/financial literacy or difficulties

age at first sex/years of education

health/education

birth weight/education

self-reported health/education

education/self-efficacy

self-efficacy/GCSE scores

child-rated school environment/GCSE scores

education/personality

personality/GCSE scores

education/Openness

education/Conscientiousness

education/motivation

education/Neuroticism

education/Extraversion

sex-specific personality effects (Aggression/Achievement Striving/Self-Control) on education

well-being/GCSE scores

education/behavioral problems

parent-rated behavior problems/GCSE scores

child-rated behavior problems/GCSE scores

independent reading/reading ability and stability

book exposure/reading ability

reading fluency/reading comprehension

longitudinal oral language/reading fluency/reading comprehension

reading/inattention

Coronary artery disease/educational attainment

Stroke: ischaemic/educational attainment

Stroke: cardioembolic/educational attainment

Stroke: large vessel disease/educational attainment

Stroke: small vessel disease/educational attainment

Type 2 diabetes/educational attainment

ADHD/educational attainment

ADHD/GCSE exam scores

ADHD/Key Stage 3 exam scores

ADHD/Key Stage 5 taking

Alzheimer's disease/educational attainment

Autism/educational attainment

Bipolar disorder/educational attainment

Major depressive disorder/educational attainment

Blood pressure: diastolic/educational attainment

Blood pressure: systolic/educational attainment

BMI/educational attainment

waist circumference/education

education/back pain

Height/educational attainment

Longevity/educational attainment

Forced expiratory volume in 1 s (FEV1)/educational attainment

Years of education/educational attainment

College degree/educational attainment

evening chronotype/educational attainment

grades or exam scores in various school subjects arts/sciences

educational subject preferences

education/developmental milestones (smiling, walking, talking, feeding oneself, daytime potty training, communicating using sentences, and night-time potty training)

highest level of mathematics class/college completion

highest level of mathematics class/years of education

highest level of mathematics class/working in a technical occupation

carry a tune/highest level of mathematics class

Eyes Test empathy score/years of college

Eyes Test empathy score/years of education

Eyes Test empathy score/intelligence

Systemizing Quotient-Revised (SQ-R)/years of college

difficulty sleeping/years of education

education/home environment

education/school environment

intelligence/criminal victimization

Psychological

food fussiness/food neophobia

dental fear/fear of pain

carry a tune/clap to a beat

carry a tune/perfect pitch

carry a tune/sing back musical notes

phonological coding/pig Latin task

phonological coding/rhyme-generation

longitudinal stability of planning/behavioral disinhibition (Porteus Maze Test)

longitudinal stability of personality

risk-taking behavior of various kinds (natural/physical, moral, financial, reproductive, competitive, safety, gambling)

Psychiatric

personality traits

personality traits/psychiatric disorders

personality traits/borderline personality disorder

intellectual disabilities

reading/math disability

reading difficulty/sex

word recognition/phonological coding/orthographic coding in the reading disabled

psychiatric illnesses/property crime

schizophrenia/epilepsy

schizophrenia/bipolar disorder

bipolar subtype 1/bipolar subtype 2/schizophrenia

schizophrenia/brain-volumes

schizophrenia/major depressive disorder

earlier-onset major depressive disorder (MDD)/adult-onset MDD/schizophrenia/bipolar disorder

Openness/schizophrenia

schizophrenia/autism

sleep/schizophrenia

tiredness/schizophrenia

self-reported health/schizophrenia

creativity/schizophrenia

age at first sex/schizophrenia

schizophrenia/HIV infection/risky sexual behavior

Empathy Quotient score/schizophrenia

self-reported sleep duration/schizophrenia

daytime sleepiness/schizophrenia

bipolar disorder/rheumatoid arthritis

bipolar disorder/type 2 diabetes

bipolar disorder/major depressive disorder

bipolar disorder/creativity

Conscientiousness/bipolar disorder

Openness/bipolar disorder

Openness/major depressive disorder

self-reported sleep duration/bipolar disorder

age at first sex/bipolar disorder

Empathy Quotient score/bipolar disorder

Systemizing Quotient-Revised (SQ-R)/bipolar disorder

brain region activation/bipolar disorder

tiredness/ADHD

major depressive disorder/ADHD

self-reported health/ADHD

autism/ADHD

Extraversion/ADHD

age at first sex/autism

Empathy Quotient score/autism

Systemizing Quotient-Revised (SQ-R)/autism

age at first sex/ADHD

ADHD/tics

ADHD/obsessive-compulsive

intracranial volume/ADHD

ADHD/bipolar disorder

tiredness/bipolar disorder

tiredness/major depressive disorder

daytime sleepiness/major depressive disorder

difficulty sleeping/major depressive disorder

self-reported health/major depressive disorder

schizophrenia/major depressive disorder

bipolar disorder/major depressive disorder

age at first sex/major depressive disorder

migraine/Neuroticism

tiredness/Neuroticism

self-reported health/Neuroticism

Grit/Conscientiousness

Conscientiousness/Extraversion

Neuroticism/Extraversion

Openness/Extraversion

Extraversion: sociability and impulsiveness facets

Social Anxiety Score/Extraversion

frequency of talking or texting on smartphone/Extraversion

Neuroticism/Conscientiousness

Openness/Conscientiousness

Openness/Neuroticism

Agreeableness/Conscientiousness

Agreeableness/Extraversion

Agreeableness/Neuroticism

Agreeableness/major depressive disorder

Conscientiousness/major depressive disorder

Conscientiousness/autism spectrum disorder

Agreeableness/autism spectrum disorder

Eyes Test empathy score/Openness

Eyes Test empathy score/self-reported empathy (Empathy Quotient)

Neuroticism, Extraversion, Psychoticism, social attitudes scale, Wilson conservatism scale longitudinal stability

Neuroticism/loneliness

Extraversion/loneliness

Extraversion/bipolar disorder

depression symptoms/loneliness

behavioral/emotional problems in children

antisocial behavior/Extraversion

antisocial behavior/Agreeableness

antisocial behavior/Conscientiousness

antisocial behavior/sensation seeking

antisocial behavior/urgency

antisocial behavior/lack of premeditation

antisocial behavior/lack of perseverance

antisocial behavior/Psychoticism

antisocial behavior/novelty seeking

antisocial behavior/impulsivity

antisocial behavior/reward dependence

antisocial behavior/depressive symptoms

longitudinal stability of antisocial symptoms

longitudinal stability of depressive symptoms

unipolar/bipolar depression

age at first sex/Alzheimers

age at first sex/risk-taking propensity

age at first sex/suffer from nerves

age at first sex/irritable personality

self-reported health/anorexia nervosa

age at first sex/anorexia nervosa

obsessive-compulsive disorder/anorexia nervosa

Bipolar disorder/anorexia nervosa

Eyes Test empathy score/anorexia nervosa

Empathy Quotient score/anorexia nervosa

Systemizing Quotient-Revised (SQ-R)/anorexia nervosa

Tourette syndrome/obsessive-compulsive disorder

hoarding/obsessive-compulsive syndrome

obsessive-compulsive disorder inventory/inventory subscales (checking, hoarding, obsessing, ordering, and washing)

excessive object acquisition/difficulties discarding possessions

compulsive hoarding/tics

obsessive-compulsive syndrome/tics

panic disorder/generalised anxiety disorder/phobias/obsessive-compulsive disorder/post-traumatic stress disorder

bulimia/anorexia nervosa

Right temporal pole surface area/anorexia nervosa

weight and shape concerns and behaviors/binge eating

obesity/binge eating

purging/binge eating

body dissatisfaction / weight preoccupation / binge eating

major depressive disorder/anorexia nervosa

Neuroticism/anorexia nervosa

Schizophrenia/anorexia nervosa

Conscientiousness/schizophrenia

Psychiatric factor/anorexia nervosa

Years of education/anorexia nervosa

College attendance/anorexia nervosa

Extreme BMI/anorexia nervosa

Body fat percentage/anorexia nervosa

Overweight/anorexia nervosa

Hip circumference/anorexia nervosa

HDL cholesterol/anorexia nervosa

Phospholipids in large HDL/anorexia nervosa

Concentration of large HDL particles/anorexia nervosa

Total lipids in large HDL/anorexia nervosa

Cholesterol esters in large HDL/anorexia nervosa

Free cholesterol in large HDL/anorexia nervosa

Total cholesterol in large HDL/anorexia nervosa

Fasting glucose/anorexia nervosa

HOMA-Beta/anorexia nervosa

Fasting insulin/anorexia nervosa

HOMA-IR/anorexia nervosa

major depressive disorder/bulimia

Right temporal pole surface area/major depressive disorder

dementia with Lewy bodies/Alzheimers

dementia with Lewy bodies/Parkinson's

Alzheimers/Parkinson's

difficulty sleeping/Alzheimer's disease

intracranial volume/Parkinson's disease

hippocampal volume/Alzheimer's disease

autism/Social and Communication Disorders Checklist

childhood sexual abuse/age at first sex

stressful life-events/psychotic events

Subjective well-being / depressive symptoms

Subjective well-being / Neuroticism

Neuroticism/major depressive disorder

Depressive symptoms / Neuroticism

menstrual symptoms/anxiety/depression/Neuroticism

life satisfaction/Neuroticism

positive affect/Neuroticism

Anxiety disorders / subjective well-being

Anxiety disorders / Neuroticism

Anxiety disorders / depressive symptoms

Autism spectrum disorder / subjective well-being

Autism spectrum disorder / Neuroticism

intracranial volume/autism spectrum disorder

Bipolar disorder / subjective well-being

Bipolar disorder / Neuroticism

Bipolar disorder / depressive symptoms

Schizophrenia / subjective well-being

Schizophrenia / Neuroticism

Schizophrenia / depressive symptoms

BMI / depressive symptoms

Coronary artery disease / depressive symptoms

Coronary artery disease/Neuroticism

general anxiety disorder/major depressive disorder

burnout/major depressive order

burnout/general anxiety disorder

major depressive disorder/phobias (agoraphobia / social / animal / situational phobia)

phobias/panic disorder/bulimia nervosa

Drug use

lifetime use of marijuana/smoking

tiredness/smoking status

sugar consumption/drug use

age at first sex/ever-smoker

age at first sex/cigarettes per day

self-reported sleep duration/cigarettes per day

difficulty sleeping/cigarettes per day

daytime sleepiness/cigarettes per day

age at first sex/smoking at onset

alcohol consumption/alcohol dependence (sex-varying correlations)

age at first sex/alcohol consumption

alcohol consumption/ventral striatum activity/ADHD

Ever-smoker / subjective well-being

Ever-smoker / neuroticism

Ever-smoker / depressive symptoms

Smoking/education

Smoking/intelligence

quitting smoking/intelligence

smoking/alcohol drinking

smoking/BMI

alcohol drinking/education

alcoholism/divorce

alcohol effects on arithmetic performance / alcohol effects on motor coordination

willingness to drive drunk/Eysenck personality scales

executive function/substance abuse/substance dependency, longitudinal

schizophrenia/marijuana use

Biological

tiredness/HDL cholesterol

tiredness/HbA1c

tiredness/triglycerides

self-reported health/systolic and diastolic blood pressure

birth weight/diastolic blood pressure

birth weight/systolic blood pressure

birth weight/total cholesterol

birth weight/HDL cholesterol

birth weight/LDL cholesterol

Triglycerides / subjective well-being

Triglycerides / neuroticism

Triglycerides / depressive symptoms

fasting insulin/triglycerides

fasting glucose/fasting triglycerides

waist-hip ratio/fasting triglycerides

fasting triglycerides/BMI

HDL/triglycerides

early puberty/fasting insulin

early puberty/lipid profiles

early puberty/bone mineral density

age at first sex/femoral neck bone mineral density

age at first sex/lumbar spine bone mineral density

age at first sex/fasting glucose

age at first sex/HDL cholesterol

age at first sex/LDL cholesterol

age at first sex/total cholesterol

age at first sex/triglycerides

age at first sex/fasting insulin

age at first sex/HbA1C

age at first sex/diastolic blood pressure

age at first sex/systolic blood pressure

fasting HDL/BMI

systolic blood pressure/BMI

spousal systolic blood pressure

waist-hip ratio/fasting glucose

waist-hip ratio/fasting insulin

waist-hip ratio/HDL

waist-hip ratio/systolic blood pressure

fasting glucose/fasting insulin

fasting glucose/HDL

fasting glucose/systolic blood pressure

fasting insulin/HDL

fasting insulin/systolic blood pressure

HDL/systolic blood pressure

liver enzymes/total cholesterol

liver enzymes/LDL cholesterol

liver enzymes/HDL cholesterol

liver enzymes/triglycerides

liver enzymes/glucose

liver enzymes/insulin

liver enzymes/HOMA-B

liver enzymes/HOMA-IR

liver enzymes/c-reactive protein

liver enzymes/alcohol consumption

cortisol/cortisone levels in child/adolescent hair

Disease

immune disorders

breast cancer / ovarian cancer / prostate cancer

tiredness/type 2 diabetes

sleep/type 2 diabetes

Type 2 diabetes/hypertension

rheumatoid arthritis/hypertension

psoriasis/type 2 diabetes

birth weight/type 2 diabetes

birth weight/2 hour glucose response

birth weight/fasting insulin

birth weight/Hb1Ac

difficulty sleeping/type 2 diabetes

oversleeping/type 2 diabetes

difficulty sleeping/fasting insulin

difficulty sleeping/fasting glucose

daytime sleepiness/HOMA-IR

daytime sleepiness/fasting insulin

difficulty sleeping/HOMA-IR

psoriasis/BMI

self-reported health/coronary artery disease

triglycerides/coronary artery disease

birth weight/coronary artery disease

self-reported health/ischaemic stroke

C-reactive protein/ischemic vascular disease

coronary artery disease/LDL

coronary artery disease/HDL

coronary artery disease/BMI

coronary artery disease/systolic blood pressure

coronary artery disease/type 1 diabetes

daytime sleepiness/coronary artery disease

difficulty sleeping/coronary artery disease

coronary artery calcification (CAC)/coronary artery disease

Lp(a)/coronary artery disease

LP-PLA2 activity/coronary artery disease

carotid plaque/coronary artery disease

vWF/coronary artery disease

FVIII/coronary artery disease

height/coronary artery disease

self-reported health/type 2 diabetes

rheumatoid arthritis/lupus

early puberty/type 2 diabetes

early puberty/cardiovascular disease

early puberty/polycystic ovary syndrome

age at first sex/rheumatoid arthritis

age at first sex/ulcerative colitis

age at first sex/Crohn's disease

Crohn's disease/ulcerative colitis

Crohn's disease/ulcerative colitis/ankylosing spondylitis/psoriasis/coeliac disease

self-reported sleep duration/Crohn's disease

difficulty sleeping/Crohn's disease

age at first sex/cardiovascular disease

age at first sex/type 2 diabetes

type 2 diabetes/Dyslipidemia

type 2 diabetes/osteoarthritis

type 2 diabetes/osteoporosis

Chronic obstructive pulmonary disease (COPD)/pulmonary fibrosis/asthma/lung function

asthma/type 2 diabetes

asthma/ADHD

cardiovascular disease/type 2 diabetes

esophageal adenocarcinoma/Barrett's esophagus

Intracranial aneurysms/abdominal aortic aneurysms/thoracic aortic aneurysms

Allergic rhinitis/asthma

Allergic rhinitis/hypertension

Allergic rhinitis/osteoarthritis

asthma/cardiovascular disease

asthma/Dyslipidemia

asthma/hypertension

asthma/osteoarthritis

cardiovascular disease/Dyslipidemia

cardiovascular disease/hypertension

cardiovascular disease/osteoarthritis

Transfer

Trans-population

schizophrenia

gene expression

rheumatoid arthritis

type 2 diabetes

Trans-cohort

depressive symptoms: GERA/PGC, GERA/UKB, UKB/PGC

neuroticism: UK Biobank (UKB) / Genetics of Personality Consortium

autism: PGC (USA)/iPSYCH (Denmark)

male/female Empathy Quotient score

male/female Systemizing Quotient-Revised (SQ-R)

male/female Eyes Test empathy score

ARIC/EHR phenotype consistencies

Trans-method

custom immunochip (iChip) SNP array/standard SNP array (comparing their estimates for the Crohn's disease/ulcerative colitis genetic correlation)

major depressive order: Psychiatric Genomics Consortium (PGC) clinical depression diagnosis/23andMe self-report depression

major depressive disorder/self-declared depression

Big Five personality traits in Genetics of Personality Consortium/23andMe cohorts

self-reported height/clinically measured height

Animal/plant

chimpanzee cognitive performance factors

egg color in cross vs pure bred chickens

Batrachochytrium dendrobatidis infection/development time in Bufo spinosus toad

Fraxinus excelsior infection by Hymenoscyphus fraxineus: severities of crown and collar symptoms

Mimulus guttatus

Chinook salmon

various rat/cattle/sheep/finch/amphipod/human/rhesus macaque/pig/inland garter snake/coastal garter snake

pigs

mice

Eucalyptus melliodora foliage chemistry

male genital length/female brain size in Eastern mosquitofish

higher alcohol preference/greater fear potentiated startle in mice

biomass/yield per plant/straw yield in Paspalum scrobiculatum

sexual antagonism in Drosophila melanogaster

size vs sugar content in tomatoes