Heritability and prevalence of specific fears and phobias in childhood

Fears and phobias are relatively common in childhood. Both environmental and genetic theories have tried to explain the etiology behind these conditions. However, data supporting the different theories are sparse. To investigate the relative importance of genetic and environmental influences on specific phobias and fears, parental reports of animal, situational, and mutilation fears and phobias were completed for 1106 pairs of 8- to 9-year-old Swedish twins. The prevalence of specific phobias was 7.3% for boys and 10.0% for girls. Genetic. shared environmental, and nonshared environmental effects contributed to individual differences in fears and phobias in young children, but the magnitude of the effects differed between sexes. Shared environmental effects contributed to a general susceptibility for fearfulness. Genetic and nonshared environmental effects, on the other hand, contributed both to the general susceptibility and specific fearfulness, even though these effects primarily were fear specific. These results indicate that both heritable factors as well as environmental factors such as trauma, vicarious learning, and/or negative information are important for differences in fearfulness and phobias--at least in children.     

Predicting change in psychopathology in youth referred to mental health services in childhood or adolescence

BACKGROUND: Little evidence is available on factors associated with persistence and change of psychopathology, and little is known about the predictive value of factors regarding change once problem behaviours exist. This study aims to evaluate change in level of scores of empirically derived problem patterns and to study factors that influence this change for children and adolescents referred to mental health services. METHOD: A referred sample (N = 1,652), aged 4 to 18 years at initial assessment, was followed up after a mean interval of 6.2 years. We used standardised information from parents, teachers and subjects, including the CBCL, YSR and TRF at both assessments. RESULTS: Subjects at follow-up scored significantly above the expected mean norm scores, although for most scores improvement was found. The strongest predicting factor for time 2 psychopathology was the corresponding time 1 score, odds ratios ranging from 1.6 to 21.7. Males and children older at intake improved more than females and younger children, respectively. CONCLUSIONS: Few child, family and treatment-related factors had additional predictive value over and above earlier psychopathology, and their contribution to the prediction of outcome was small. Findings indicate continuity of behavioural and emotional problems in clinically referred children and adolescents, and these problems should be viewed as chronic conditions. Girls referred for behavioural and emotional problems may form a group especially at risk for poor outcome.     

Anger/frustration, task persistence, and conduct problems in childhood: a behavioral genetic analysis

BACKGROUND: Individual differences in conduct problems arise in part from proneness to anger/frustration and poor self-regulation of behavior. However, the genetic and environmental etiology of these connections is not known. METHOD: Using a twin design, we examined genetic and environmental covariation underlying the well-documented correlations between anger/frustration, poor attention regulation (i.e., task persistence), and conduct problems in childhood. Participants included 105 pairs of MZ twins and 154 pairs of same-sex DZ twins (4-8 year olds). Independent observers rated child persistence and affect based on behavior during a challenging in-home cognitive and literacy assessment. Teachers and parents provided reports of conduct problems. RESULTS: Persistence, anger/frustration, and conduct problems included moderate heritable and nonshared environmental variance; conduct problems included moderate shared environmental variance as well. Persistence and anger/frustration had independent genetic covariance with conduct problems and nonshared environmental covariance with each other. CONCLUSIONS: The findings indicate genetically distinct though inter-related influences linking affective and self-regulatory aspects of temperament with behavior problems in childhood.     

Developmental trajectories of depressive symptoms from early childhood to late adolescence: gender differences and adult outcome

BACKGROUND: Limited information is available on gender differences and young-adult poor outcome in children and adolescents following distinct developmental trajectories of depressive symptoms. METHODS: Parent information on depressive symptoms of 4- to 18-year-olds from an ongoing Dutch community-based longitudinal multiple-cohort study (N = 2,076) was used to estimate trajectories from semi-parametric mixture models. The identified trajectories were used to predict depressive problems, general mental health problems, referral to mental health care, and educational attainment in young adulthood. RESULTS: In both genders six distinct developmental trajectories were identified. Gender differences existed not only in level, but also in shape and timing of onset of depressive problems. Only in girls was a chronic trajectory of early childhood-onset depression identified. In both boys and girls a group with increasing levels of depressive symptoms was identified that reached a high level around adolescence, although boys showed an earlier onset. Two decreasing trajectories were found in boys, one reaching normative levels of depressive symptoms around late childhood and one around mid-adolescence, while none was found for girls. Individuals who followed elevated trajectories during their whole childhood or starting at adolescence had significantly more depressive and other mental health problems in young adulthood compared to those who followed normative trajectories. Boys in these elevated trajectories showed lower educational attainment, while girls were more likely to have been referred to mental health care. CONCLUSIONS: This study shows the value of estimating growth-mixture models separately for boys and girls. Girls with early childhood or adolescence-onset depressive problems and boys with depressive problems during childhood or starting in adolescence are especially at risk for poor outcome as young adults and should be considered candidates for intervention.     

Genetic and environmental influences on victims, bullies and bully-victims in childhood

BACKGROUND: Three groups of children are involved in bullying: victims, bullies and bully-victims who are both bullies and victims of bullying. Understanding the origins of these groups is important since they have elevated emotional and behavioural problems, especially the bully-victims. No research has examined the genetic and environmental influences on these social roles. METHOD: Mother and teacher reports of victimisation and bullying were collected in a nationally representative cohort of 1,116 families with 10-year-old twins. Model-fitting was used to examine the relative influence of genetics and environments on the liability to be a victim, a bully or a bully-victim. RESULTS: Twelve percent of children were severely bullied as victims, 13% were frequent bullies, and 2.5% were heavily involved as bully-victims. Genetic factors accounted for 73% of the variation in victimisation and 61% of the variation in bullying, with the remainder explained by environmental factors not shared between the twins. The covariation between victim and bully roles (r = .25), which characterises bully-victims, was accounted for by genetic factors only. Some genetic factors influenced both victimisation and bullying, although there were also genetic factors specific to each social role. CONCLUSIONS: Children's genetic endowments, as well as their surrounding environments, influence which children become victims, bullies and bully-victims. Future research identifying mediating characteristics that link the genetic and environmental influences to these social roles could provide targets for intervention.     

Assessing the effects of age,sex and shared environment on the genetic aetiology of depression in childhood and adolescence

BACKGROUND: Depressive symptoms and disorder are experienced by a significant proportion of young people and have long-lasting deleterious effects. The aims of the current investigation were to examine the aetiology of depressive symptoms using a twin design. In particular to examine the effects of sex, age, maternal depression and anxiety symptoms and to examine the aetiology of high depression scores. METHODS: Questionnaires were sent to the families of a population-based sample of twins aged between 8 and 17 years. Parents and children over the age of 11 were asked to complete the Mood and Feelings Questionnaire and Hospital Anxiety and Depression Scale (mothers only). Responses were obtained from 1463 families and data were analysed using genetic model fitting and DeFries and Fulker regression analysis. RESULTS: Depressive symptoms, particularly when self-rated, were significantly genetically influenced. There was evidence of significant heterogeneity according to age, with shared environmental factors more important and genetic factors less important for children aged 8 to 10 than for adolescents aged 11 to 17 years. Some but not all of the shared environmental influences on parent-rated depressive symptoms were accounted for by maternal symptoms of depression and anxiety. There was a significant effect of gender for self-rated depressive symptoms. For boys, genetic factors were of greater importance and common environmental influences of less importance than for girls. Shared environmental effects had a substantial influence on high self-rated depression scores. Adolescents who scored highly on self-rated depression questionnaires experienced significantly more shared life events and their mothers had significantly higher internalising symptoms than adolescents who scoredwithin the normal range. CONCLUSIONS: The results of this study add to the evidence that the aetiology of depressive symptoms differs by age, with genetic factors becoming more important from childhood to adolescence. Some but not all of the shared environmental effect observed for mother-rated depression scores is due to maternal depression and anxiety symptoms. For self-rated depressive symptoms, the importance of genetic and environmental factors may also differ by sex, with genetic influences more important for boys. The aetiology of high depression symptom scores, when self-rated, appears to differ from scores within the normal range in that shared environmental factors appear to be more important. Further research is needed to identify these shared environmental factors using longitudinal models that test genetic and environmental mediation.     

Developmental‐genetic effects on level and change in childhood fears of twins during adolescence

Background: If the adaptive significance of specific fears changes with age, the genetic contribution to individual differences may be lowest at the age of greatest salience. The roles of genes and environment in the developmental‐genetic trajectory of five common childhood fears are explored in 1094 like‐sex pairs of male and female monozygotic and dizygotic twins assessed on up to three occasions during adolescence (ages 8–18 years). Methods: Dichotomous self‐ratings of a cluster of five correlated fears from Ollendick’s schedule of fears (FSSC‐R) were extracted for subjects at each occasion of assessment. The effects of genes and environment on overall level of fears and rates of adolescent decline were explored by fitting an item‐response theory (‘IRT’) model that allowed for individual genetic and environmental differences in initial fear level (‘intercept’) and rates of adolescent change (‘slope’) across the repeated waves of measurement. Different forms of the model were explored using Markov Chain Monte Carlo (MCMC) methods to derive the posterior distribution of subject and item parameters from the raw responses. Results: Additive genetic differences affect the common factor underlying the five fear‐items. The same genes also affect rates of change with age, especially in boys. Male adolescents with higher overall genetic predisposition to childhood fears tended to show slower recovery with age than subjects with relatively low initial values. Thus, the genetic variance apparently increases with age. Conclusions: This finding is consistent with a prediction that the regulation of genetic differences will be strongest, and thus the additive genetic variance will be smallest, at the age when the particular stimulus is most salient. Items differed in the extent to which they were sensitive to underlying random differences in the rate of developmental change. Individual differences in rates of change with age were more marked in boys than girls.     

Using sex differences in psychopathology to study causal mechanisms: unifying issues and research strategies

BACKGROUND: Although there is an extensive literature, both speculative and empirical, on postulated differences between males and females in their rates of particular types of disorder, very little is known about the mechanisms that underlie these sex differences. The study of mechanisms is important because it may provide clues on aetiological processes. The review seeks to outline what is known, what are the methodological hazards that must be dealt with, and the research strategies that may be employed. METHODS: We note the need for representative general samples, and for adequate measurement and significance testing if valid conclusions are to be drawn. We put forward three levels of causes that have to be considered: a genetically determined distal basic starting point; the varied consequences of being male or female; and the proximal risk or protective factors that are more directly implicated in the causal mechanisms that predispose to psychopathology. In delineating these, we argue that three key sets of evidential criteria have to be met: a) that the risk factors differ between males and females; b) that they provide for risk or protection within each sex; and c) that when introduced into a causal model, they eliminate or reduce the sex differences in the disorders being studied. RESULTS: A male excess mainly applies to early onset disorders that involve some kind of neurodevelopmental impairment. A female excess mainly applies to adolescent-onset emotional disorders. No variables have yet met all the necessary criteria but some good leads are available. The possible research strategies that may be employed are reviewed. CONCLUSIONS: The systematic investigation of sex differences constitutes an invaluable tool for the study of the causal processes concerned with psychopathology.     

Negative life events as an account of age-related differences in the genetic aetiology of depression in childhood and adolescence

BACKGROUND: Many twin studies have reported that the genetic aetiology of depression differs according to age, with genetic influences being more important for adolescents than younger children. We sought to examine whether this age-related increase in the relative importance of genetic factors is due to an increase in gene-environment correlation specifically involving negative life events. METHOD: Questionnaires were sent to the families of a population-based sample of twins aged between 8 and 17 years. Parents of all the twins and adolescents aged 11 and over were asked to complete the Mood and Feelings Questionnaire (Costello & Angold, 1988) and a modified version of the Life Events Checklist (Johnson & McCutcheon, 1980). Responses were obtained from 1468 families and data were analysed using genetic model fitting. Bivariate analysis of 1) negative life events and 2) behaviour-dependent life events and depression symptoms was undertaken separately for children (aged 8 to 10 years) and adolescents (aged 11 to 17 years). Differences in genetic and environmental parameters across age groups were tested. RESULTS: Adolescence was associated with a greater number of behaviour-dependent life events. Genetic covariation of negative life events and depression was greater for adolescents than for children. CONCLUSIONS: Bivariate model fitting was consistent with the greater heritability of depression seen in adolescence being due to an increase in gene-environment correlation involving negative life events. However, the effects of genes associated specifically with maturation in adolescence, the possibility of 'person' effects and the role of other environmental factors also need to be considered.     

The development of impulsivity,fearfulness, and helpfulness during childhood: patterns of consistency and change in the trajectories of boys and girls

BACKGROUND: The objective of the present study was to describe the development of boys and girls during the elementary-school years on three dimensions that conceptually and empirically represent risk for maladjustment. METHOD: Every year between kindergarten and grade six, teachers rated the impulsivity, fearfulness, and helpfulness dimensions among a sample of 1,865 children representative of kindergarten boys and girls in the province of Quebec (Canada) in 1986-87. A group-based trajectory method was used to 1) identify groups of boys and girls following distinct-level trajectories of behaviours (on each dimension) during the elementary-school years; 2) estimate the proportion of children in each of the identified trajectory groups; and 3) estimate the patterns of consistency and variations in trajectories. RESULTS: The results indicated that the best models comprised three distinct-level trajectory groups on fearfulness and helpfulness (a low, moderate, and high group) and four distinct-level trajectory groups on impulsivity. The helpfulness and fearfulness trajectory groups were generally more stable than the impulsivity groups. The broad patterns of development were similar across sexes. However, there were more boys on the higher impulsivity trajectories and low helpfulness trajectory, while there were more girls on the high fearfulness trajectory. CONCLUSION: We found that behavioural consistency over middle childhood varied across trajectory groups and across dimensions, and we identified sex differences in the distribution of children in the different trajectory groups that may reflect gender-specific risks for psychopathology.     

Positive and protective: effects of early theory of mind on problem behaviors in at-risk preschoolers

Background:  Exposure to harsh parenting and children's skills in 'Theory of Mind' (ToM) show independent and interacting associations with problem behaviors at age 2 ( Hughes & Ensor, 2006 ). This study examined whether these age-2 measures also predict age-4 problem behaviors.
Method:  In a socially diverse sample ( N  = 120), multi-informant, multi-measure, multi-setting ratings indexed problem behaviors at ages 2, 3 and 4; children completed both ToM and verbal-ability tasks at age 2, while video-based ratings of maternal negative affect and control within dyadic mother-child play indexed harsh parenting.
Results:  Age-2 harsh parenting and ToM were independent and interacting predictors of age-4 problem behaviors, even with age-2 problem behaviors, verbal ability and social disadvantage all controlled. The interaction between harsh parenting and ToM distinguished persistent vs. diminishing problem behaviors.
Conclusions:  Both child and family characteristics predict increases in problem behaviors from 2 to 4; adverse effects of harsh parenting are attenuated for children with good ToM skills.     

A longitudinal study of body fatness in childhood and adolescence.

Data from the United States Health Examination Surveys were analyzed to determine changes in body fatness between childhood and adolescence. A national probability sample (2,177 children) was examined in both Cycle II (6 to 11 years) and Cycle III (12 to 17 years) of these surveys and comprised the study cohort. The interval between examinations was three or four years. Adiposity was measured as skinfold thickness and correlations between childhood and adolescent adiposity were explored. High rank-order correlations were found between the two examinations for each race-sex group (P less than 0.001). The relationship between childhood and adolescent fatness was independent of stature, skeletal and sexual maturation, and economic status. Childhood fatness was the most predictive factor for adolescent fatness. This strong relationship indicates that the potentially obese adolescent can be identified during childhood.