Early Puberty Is Associated With Higher Academic Achievement in Boys and Girls and Partially Explains Academic Sex Differences

Purpose: On average, boys have lower academic achievement than girls. We investigated whether the timing of puberty is associated with academic achievement, and whether later puberty among boys contributes to the sex difference in academic achievement. Method: Examination scores at age 16 were studied among 13,477 British twins participating in the population-based Twins Early Development Study. A pubertal development scale, a height based proxy of growth spurt, and age at menarche were used as indicators of puberty. Associations between puberty, sex, and academic achievement were estimated in phenotypic mediation models and biometric twin models. Results: Earlier puberty was associated with higher academic achievement both in boys and girls. The exception was early age at menarche in girls, which associated with lower academic achievement. More than half of the sex differences in academic achievement could be linked to sex differences in pubertal development, but part of this association appeared to be rooted in prepubertal differences. The biometric twin modelling indicated that the association between puberty and academic achievement was due to shared genetic risk factors. Genetic influences on pubertal development accounted for 7%-8% of the phenotypic variation in academic achievement. Conclusions: Pubertal maturation relates to the examination scores of boys and of girls. This can give genes related to pubertal maturation an influence on outcomes in education and beyond. Sex differences in pubertal maturation can explain parts of the sex difference in academic achievement. Grading students when they are immature may not accurately measure their academic potential. (c) 2021 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Social inequalities in reception of social welfare support: A population based twin study

Social welfare support runs in families. Recent studies using Nordic registry data have found individual differences in genetic factors to be of substantial importance for medical benefits. However, to date there has been no genetically informative studies on receiving social welfare support. To prevent young adults to not drop out of the work life and become recipients of social welfare support, it is of substantial interest to clarify to what extent the familiarity of social welfare support is due to genetic or social differences between families. We used data from the Historical-Event Database on 7,698 Norwegian twins born 1967-1979 to estimate the relative contribution of genetic factors, the effective familial environment (i.e. the “shared environment”), and individual-specific environmental factors. We found that the two forms of familial risk, genetic and shared environmental, explained 39% and 45%, respectively, of the risk for receiving social welfare support among young Norwegian twins. Only 17% of the variance in risk factors could be explained by individual-specific risk factors. It appears that risk for receiving social welfare support can to a great extent be explained by environmental differences between families. Therefore prevention strategies targeting social inequalities between families would indeed be effective. Furthermore, genetic risk factors are also important in explaining risk for receiving social welfare support. These effects could be mediated through heritable traits related to substance abuse, psychiatric disorders, and personality. Individual-specific risk factors were of very little importance. Hence, with regard to receiving social welfare support, family matters

Genetic and Environmental Structure of DSM-IV Criteria for Antisocial Personality Disorder: A Twin Study

Results from previous studies on DSM-IV and DSM-5 Antisocial Personality Disorder (ASPD) have suggested that the construct is etiologically multidimensional. To our knowledge, however, the structure of genetic and environmental influences in ASPD has not been examined using an appropriate range of biometric models and diagnostic interviews. The 7 ASPD criteria (section A) were assessed in a population-based sample of 2794 Norwegian twins by a structured interview for DSM-IV personality disorders. Exploratory analyses were conducted at the phenotypic level. Multivariate biometric models, including both independent and common pathways, were compared. A single phenotypic factor was found, and the best-fitting biometric model was a single-factor common pathway model, with common-factor heritability of 51% (95% CI 40–67%). In other words, both genetic and environmental correlations between the ASPD criteria could be accounted for by a single common latent variable. The findings support the validity of ASPD as a unidimensional diagnostic construct

Caffeine Consumption, Toxicity, Tolerance and Withdrawal; Shared Genetic Influences With Normative Personality and Personality Disorder Traits

Public Health Significance Both the amount of caffeine people consume and their response to caffeine is heritable. A modest proportion of the genetic influences underlying caffeine use and response is shared with personality and personality disorder traits. Our main aim was to estimate the extent of overlapping etiology between caffeine consumption and response and normative and pathological personality. Linear mixed-effects models were used to identify normative personality domains and personality disorder (PD) traits for inclusion in multivariate twin analyses together with individual caffeine related measures. Data were obtained from Norwegian adult twins in a face-to-face interview conducted in 1999-2004 as part of a population-based study of mental health and through self-report in 2010-2011 and 2015-2017. Personality disorder data was available for 2,793 twins, normative personality for 3,889 twins, and caffeine for 3,862 twins (mean age 43.0 years). Normative personality was assessed using the self-reported Big Five Inventory, PD traits were assessed by the Structured Interview for DSM-IV Personality, and caffeine consumption, toxicity, tolerance, and withdrawal were assessed through a self-report questionnaire developed at the Norwegian Institute of Public Health. Caffeine measures were found to be moderately heritable, h(2) = 30.1%-45.0%. All normative personality domains and four PD traits, antisocial, borderline, dependent and paranoid, were significantly associated with at least one caffeine variable. A small proportion of variance in caffeine consumption was attributable to genetic factors shared with normative personality (1.3%) and personality disorders (11.4%). A modest proportion of variance in caffeine tolerance and toxicity was attributable to genetic factors shared with both normative personality (26.9%, 24.8%) and personality disorders (21.0%, 36.0%). The present study found caffeine consumption and response to be heritable and provides evidence that a small to-modest proportion of this genetic etiology is shared with both normative and pathological personality.Peer reviewe

The educational burden of disease: a cohort study

Background Students with health disorders might be at risk of disengaging from education, which can reinforce socioeconomic inequalities in health. We aimed to evaluate the associations between 176 diseases and injuries and later school performance in Norwegian adolescents and to estimate the importance of each disorder using a novel measure for the educational burden of disease (EBoD). Methods We used diagnostic information from government-funded health services for all Norwegian inhabitants who were born between Jan 1, 1995, and Dec 31, 2002, were registered as living in Norway at age 11–16 years, and were participating in compulsory education. School performance was assessed as grade point average at the end of compulsory education at age 16 years. We used a linear regression of school performance on disease in a fixed-effects sibling comparison model (113 411 families). The association (regression coefficients) between disease and school performance was multiplied by disease prevalence to estimate the proportional EBoD among 467 412 individuals participating in compulsory education. Findings Overall, although most diseases were not meaningfully associated with grade point average (regression coefficients close to 0), some were strongly associated (eg, intellectual disability regression coefficients –1·2 for boys and –1·3 for girls). The total educational disease burden was slightly higher for girls (53·5%) than for boys (46·5%). Mental health disorders were associated with the largest educational burden among adolescents in Norway (total burden 44·6%; boys 24·6% vs girls 20·0%), of which hyperkinetic disorder contributed to 22·1% of the total burden (boys 14·6% vs girls 7·5%). Among somatic diseases, those with unknown causes and possibly mental causes were associated with the largest educational burden. Interpretation The EBoD concept could provide a simple metric to guide researchers and policy makers. Because mental health disorders form a large component of the educational burden, investment in mental health might be particularly important for improving educational outcomes in adolescents.publishedVersio

Socioeconomic status and sick leave granted for mental and somatic disorders: a prospective study of young adult twins

Background Low socioeconomic status (SES), indicated by low income and education, has consistently been found to be a strong predictor of sick leave. Several possible pathways from SES to sick leave have been described in previous literature, but there are also evidence indicating that the association can be confounded by common underlying factors. This study utilizes a population-based sample of employed young adult twins to estimate (i) the degree to which education and income are prospectively related to sick leave granted for mental, somatic, and any disorder, and (ii) whether these associations are confounded by familial factors. Methods Registry data on educational attainment and income at age 30 and subsequent sick leave were available for 6,103 employed young adult twins, among which there were 2,024 complete twin pairs. The average follow-up time was 6.57 years. Individual-level associations and fixed effects within twin pairs were estimated. Results Low education and income were associated with sick leave granted for both mental and somatic disorders, and with sick leave granted for any disorder. Associations were attenuated within dizygotic twin pairs and reduced to non-significance within monozygotic twin pairs, suggesting influence of familial factors on the associations between SES and sick leave. Conclusions Low SES is associated with a higher level of sick leave granted for both mental and somatic disorders among young adults, but these associations are confounded by factors that are common to co-twins. Education and income are therefore not likely to strongly affect sick leave in young adulthood

Specific Antisocial and Borderline Personality Disorder Criteria and General Substance Use : A Twin Study

Antisocial (ASPD) and borderline (BPD) personality disorders (PDs) are associated with increased risk for substance use. They are "specific" risk factors among PDs in that they withstand adjusting for the other PDs, whereas the reverse does not hold. Specificity is a classic sign of causation. This empirical work addresses 3 further problems that can undermine causal inferences in personality and substance-use research: hierarchical nature of etiologic factors in psychiatry, imperfectly operationalized PD criteria, and possible genetic or environmental confounding, as seen in lack of "etiologic continuity." We used exploratory structural equation bifactor modeling and biometric models to mitigate these problems. The participants were Norwegian adult twins of ages 19-36 years (N = 2,801). Criteria for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), PDs were assessed using a structured interview. General substance-use risk was indicated by World Health Organization Composite International Diagnostic Interviewed alcohol use disorder and illicit drug use, and by self-reported regular smoking. A general risk factor for all criteria of both ASPD and BPD was the strongest individual correlate of general substance use and showed etiologic continuity, though just 3 specific PD criteria could predict substance use to the same extent. The findings indicate that a broad latent factor for both ASPD and BPD may be a specific and a genetically and environmentally unconfounded risk factor for substance use. Substance-use treatment research might benefit from attending to transdiagnostic models of ASPD, BPD, and related behavioral disinhibition.Peer reviewe