Epigenome-wide DNA methylation in externalizing behaviours: A review and combined analysis

DNA methylation (DNAm) is one of the most frequently studied epigenetic mechanisms facilitating the interplay of genomic and environmental factors, which can contribute to externalizing behaviours and related psychiatric disorders. Previous epigenome-wide association studies (EWAS) for externalizing behaviours have been limited in sample size, and, therefore, candidate genes and biomarkers with robust evidence are still lacking. We 1) performed a systematic literature review of EWAS of attention-deficit/hyperactivity disorder (ADHD)- and aggression-related behaviours conducted in peripheral tissue and cord blood and 2) combined the most strongly associated DNAm sites observed in individual studies (p < 10^-3) to identify candidate genes and biological systems for ADHD and aggressive behaviours. We observed enrichment for neuronal processes and neuronal cell marker genes for ADHD. Astrocyte and granulocytes cell markers among genes annotated to DNAm sites were relevant for both ADHD and aggression-related behaviours. Only 1 % of the most significant epigenetic findings for ADHD/ADHD symptoms were likely to be directly explained by genetic factors involved in ADHD. Finally, we discuss how the field would greatly benefit from larger sample sizes and harmonization of assessment instruments.

Educational level, attention problems, and externalizing behaviour in adolescence and early adulthood: the role of social causation and health-related selection-the TRAILS study

Social causation and health-related selection may contribute to educational differences in adolescents' attention problems and externalizing behaviour. The social causation hypothesis posits that the social environment influences adolescents' mental health. Conversely, the health-related selection hypothesis proposes that poor mental health predicts lower educational attainment. From past studies it is unclear which of these mechanisms predominates, as attention problems and externalizing behaviour have the potential to interfere with educational attainment, but may also be affected by differences in the educational context. Furthermore, educational gradients in mental health may reflect the impact of 'third variables' already present in childhood, such as parental socioeconomic status (SES), and IQ. We investigated both hypotheses in relation to educational differences in externalizing behaviour and attention problems throughout adolescence and young adulthood. We used data from a Dutch cohort (TRAILS Study; n = 2229), including five measurements of educational level, externalizing behaviour, and attention problems from around age 14-26 years. First, we evaluated the directionality in longitudinal associations between education, externalizing behaviour, and attention problems with and without adjusting for individual differences using fixed effects. Second, we assessed the role of IQ and parental SES in relation to attention problems, externalizing behaviour, and educational level. Attention problems predicted decreases in education throughout all of adolescence and young adulthood. Differences in parental SES contributed to increases in externalizing behaviour amongst the lower educational tracks in mid-adolescence. Childhood IQ and parental SES strongly predicted education around age 14. Parental SES, but not IQ, also predicted early adolescent attention problems and externalizing behaviour. Our results provide support for the health-related selection hypothesis in relation to attention problems and educational attainment. Further, our results highlight the role of social causation from parental SES in determining adolescent educational level, attention problems, and externalizing behaviour.

The characteristics and factors of the internalizing and externalizing behaviours of children at high risk for autism spectrum disorder

BACKGROUND

The behavioral characteristics of children with autism spectrum disorder (ASD) are not only affected by their disease, but also by their parenting environment. HR-ASD has the risk of developing internalization and externalization problems. How the early development of these behavioral problems is affected by parent-child interaction is worth exploring. We tested whether parent-child interactions and parenting characteristics were associated with behavioural problems during the infant periods.

METHODS

This study collected data from 91 infants at high risk for ASD and 68 matched typically developing (TD) infants, about their internalizing and externalizing behavioural problems and engagement states (i.e. positive, negative, and parent-child interactions), using free play paradigm. Parent measures were assessed using the Broad Autism Phenotypic Questionnaire (BAPQ) and Parenting Stress Index Short Form (PSI-SF) questionnaire. The core symptoms of ASD were assessed using the the Autism Diagnostic Observational Schedule (ADOS).

RESULTS

During free play, infants in the HR-ASD group showed more internalizing (P < 0.001) and externalizing (P < 0.05) behaviours and less positive engagement (P < 0.01) than the TD group. In the regression analysis, we found that parenting stress had an impact on the infants' externalizing behaviours (△R2 = 0.215). Parent negative engagement had an impact on the infants' internalizing behaviours (△R2 = 0.451).

CONCLUSIONS

The present study revealed that children at high risk for ASD exhibited more severe internalizing and externalizing behavioural problems than TD group. The parent negative engagement is associated with behavioural problems. The findings on the contribution of parents' factors to behavioural problems suggests that the parenting stress and parent-child interactions are important factors for mitigating behavioural problems.

Statistical analysis of childhood and early adolescent externalizing behaviors in a middle low income country

The article show the pattern of externalizing behavior across age, gender, school type, and school level, with reference to aggression, delinquency, and hyperactivity. The study samples were primary school pupils and secondary school students from three selected Local Government Areas (LGA) in Ogun State, Nigeria [Ado-Odo/Ota, Ifo, and Yewa South]. Their ages ranged from 10 to 20 years. The student/pupil sample was 1770 in all. The instrument used was an adapted version of Achenbach's child behavior checklist and youth self-report. Basic descriptive statistics like frequency, percentage, mean, standard deviation, as well as non-parametric statistics like Phi-coefficient, Chi-square, Goodman and Kruskal's gamma, Mann Whitney U test and Kruskal Wallis H test were utilized. Inferential parametric statistics like Pearson r, analysis of variance and simple regression were also utilized. Four major findings were reported. Firstly, the private schools irrespective of age, gender and level, scored higher than the public school in aggression, delinquency, and hyperactivity. Secondly, aggression is higher in secondary schools, while delinquency and hyperactivity are more prevalent in primary schools. Thirdly, school level and school type are the strongest predictors of externalizing behavior. Lastly, correspondence analysis showed a similar behavioral pattern for the three behaviors and three distinct behavioral patterns. i). Respondents aged 10 and below and those in primary schools (ii). Male, public and between 16 and 20. iii). Private, secondary, female and between 11 and 15. Implications of the study are discussed.

The Mediation of Maternal Occupational Skillfulness on Maternal Education and Chinese Preschoolers' Behavior

There is growing evidence supporting the individual associations of maternal occupation and maternal education with children's behavioral outcomes. However, few studies have linked these factors together in a mediation model. The current study is the first to examine the mediating effect of maternal occupational skillfulness on the relationship between the length of maternal education and preschool children's behavioral outcomes in the Chinese context. To assess children's behavior, parents and teachers of 286 preschoolers from the China Jintan Cohort Study completed the Child Behavior Checklist (CBCL) and Caregiver-Teacher Report Form (C-TRF), respectively. Sociodemographic information, such as maternal occupational skillfulness and education level, was also collected. Using PROCESS and kappa statistics, maternal occupational skillfulness was found to mediate the effect of length of maternal education on both internalizing and externalizing behaviors of preschoolers, as rated by parents but not on behaviors as rated by teachers. Such findings can provide insight for counseling psychologists or family therapists in providing mothers, particularly those in low-skill jobs, appropriate advice and strategies for handling job-related stress. Mother-child relationships would consequently improve, which could then minimize the development of children's internalizing and externalizing behaviors. Furthermore, teachers could identify at-risk children and provide early intervention. Our findings also offer insight for policy makers to consider legislation providing financial assistance from the government to low-income mothers. Future replication studies should be conducted in other countries so as to determine whether similar results can be obtained.