A Comparison of Heritability Estimates by Classical Twin Modeling and Based on Genome-Wide Genetic Relatedness for Cardiac Conduction Traits.

Twin studies have found that ~50% of variance in electrocardiogram (ECG) traits can be explained by genetic factors. However, genetic variants identified through genome-wide association studies explain less than 10% of the total trait variability. Some have argued that the equal environment assumption for the classical twin model might be invalid, resulting in inflated narrow-sense heritability (h 2) estimates, thus explaining part of the 'missing h 2'. Genomic relatedness restricted maximum likelihood (GREML) estimation overcomes this issue. This method uses both family data and genome-wide coverage of common SNPs to determine the degree of relatedness between individuals to estimate both h 2 explained by common SNPs and total h 2. The aim of the current study is to characterize more reliably than previously possible ECG trait h 2 using GREML estimation, and to compare these outcomes to those of the classical twin model. We analyzed ECG traits (heart rate, PR interval, QRS duration, RV5+SV1, QTc interval, Sokolow-Lyon product, and Cornell product) in up to 3,133 twins from the TwinsUK cohort and derived h 2 estimates by both methods. GREML yielded h 2 estimates between 47% and 68%. Classical twin modeling provided similar h 2 estimates, except for the Cornell product, for which the best fit included no genetic factors. We found no evidence that the classical twin model leads to inflated h 2 estimates. Therefore, our study confirms the validity of the equal environment assumption for monozygotic and dizygotic twins and supports the robust basis for future studies exploring genetic variants responsible for the variance of ECG traits.

The state effect of depressive and anxiety disorders on big five personality traits.

BACKGROUND: Neuroticism and extraversion are affected by depressive disorder state. Less is known about depressive state effects on conscientiousness, agreeableness and openness. Furthermore, state effects of anxiety disorders on personality have been far less studied than those of depressive disorder. Here, we aim to determine the extent of change in all five personality traits associated with the occurrence of or recovery from depressive and anxiety disorders. METHODS: Using the Composite International Diagnostic Interview (CIDI) at baseline and two-year follow-up, respondents from the Netherlands Study of Depression and Anxiety (NESDA) were divided into four groups: unaffected at baseline and follow-up, occurrence, recovery, and affected at baseline and follow-up. Personality change (NEO-five factor inventory) was examined in the occurrence and recovery groups relative to the unaffected and affected groups, respectively. Analyses were repeated, differentiating between (specific) depressive and anxiety disorders. RESULTS: We found small state effects of affective disorders on neuroticism, extraversion and conscientiousness. Corrected for each other, both depressive and anxiety disorders showed small state effects on neuroticism, but effects on extraversion and conscientiousness were mainly associated with depressive disorders. CONCLUSIONS: State effects were small. When assessing neuroticism, the presence of both depressive and anxiety disorders should be taken into account, as both may independently increase neuroticism scores. However, when assessing extraversion and conscientiousness, depressive disorders but not anxiety disorders are likely to be of influence. Agreeableness and openness are influenced by neither.