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Background: Recent evidence suggests that impaired foetal growth may provide an early indication of increased risk of child attention problems. However, despite both foetal growth and child attention problems differing by sex, few studies have examined sex differences in this association. Furthermore, no studies have been conducted in low- and middle-income countries, where there are higher rates of perinatal problems. This study aimed to test for sex differences in the association between foetal growth indices and attention problems at age four, in a large, prospective birth cohort from a middle-income country. Methods: A total of 3,749 neonates from the 2004 Pelotas birth cohort (Brazil) with foetal growth indices collected at birth [low birthweight (LBW), small-for-gestational age (SGA), head circumference (HC), head circumference-to-abdominal circumference ratio (HC/AC) and ponderal index (PI)], were assessed for attention problems using the Child Behaviour Checklist at age four. Ordinal logistic regression with successive adjustment for maternal, demographic, gestational, perinatal and child nutrition/mother-child morbidity, was conducted separately for girls and boys. Results: In girls, attention difficulties were associated with being born SGA (OR = 1.40, CI = 1.08-1.82, p = 0.012), with a small HC (OR = 1.52, CI = 1.11-2.08, p = 0.009), or with a low PI (OR = 1.29, CI = 1.08-1.54, p = 0.005). There were no associations identified between attention difficulties and any foetal growth indices in boys. Conclusions: Our results show that girls with impaired foetal growth may be particularly at risk of attention difficulties in childhood. This is consistent with emerging research that female foetuses may be more vulnerable to certain suboptimal intrauterine environments, inducing epigenetic changes that lead to disturbed growth and long-term developmental impairment.

Background: Many low- and middle-income countries have high levels of violence. Research in high-income countries shows that risk factors in the perinatal period are significant precursors of conduct problems which can develop into violence. It is not known whether the same early influences are important in lower income settings with higher rates of violence. This study compared perinatal and sociodemographic risk factors between Brazil and Britain, and their role in explaining higher rates of conduct problems and violence in Brazil. Methods: Prospective population-based birth cohort studies were conducted in Pelotas, Brazil (N = 3,618) and Avon, Britain (N = 4,103). Eleven perinatal and sociodemographic risk factors were measured in questionnaires completed by mothers during the perinatal period. Conduct problems were measured in questionnaires completed by mothers at age 11, and violence in self-report questionnaires completed by adolescents at age 18. Results: Conduct problems were predicted by similar risk factors in Brazil and Britain. Female violence was predicted by several of the same risk factors in both countries. However, male violence in Brazil was associated with only one risk factor, and several risk factor associations were weaker in Brazil than in Britain for both females and males. Almost 20% of the higher risk for conduct problems in Brazil compared to Britain was explained by differential exposure to risk factors. The percentage of the cross-national difference in violence explained by early risk factors was 15% for females and 8% for males. Conclusions: A nontrivial proportion of cross-national differences in antisocial behaviour are related to perinatal and sociodemographic conditions at the start of life. However, risk factor associations are weaker in Brazil than in Britain, and influences in other developmental periods are probably of particular importance for understanding male youth violence in Brazil.

Background: The study of gene-environment interactions (G by E) is one of the most promising strategies to uncover the origins of mental disorders. Replication of initial findings, however, is essential because there is a strong possibility of publication bias in the literature. In addition, there is a scarcity of research on the topic originated from low- and middle-income countries (LMIC). The aim of this study was to replicate G by E hypotheses for externalizing problems among adolescents in a middle-income country. Methods: As part of the Pelotas 1993 Birth Cohort Study, 5,249 children were enrolled at birth and followed up to the age of 15 years, with an 85.7% retention rate. We sought an interaction between the homozygosity of the 10-repeat allele at the dopamine transporter ("DAT1") gene and prenatal maternal smoking in the development of hyperactivity problems during adolescence assessed by the Strengths and Difficulties Questionnaire. We also tested for an interaction between the uVNTR polymorphism at the monoamine oxidase A ("MAOA") and the experience of childhood maltreatment in the occurrence of conduct problems among adolescent boys. Results: Although there was a clear association between prenatal maternal smoking and hyperactivity scores in adolescence ("p" less than 0.001), no main genetic or interaction effects for the "DAT1" gene were detected. Similarly, childhood maltreatment showed to be associated with conduct problems among boys ("p" less than 0.001), with no observable main genetic or interaction effects for the "MAOA" gene. Conclusions: In the largest mental health G by E study performed in a LMIC to date, we did not replicate previous positive findings from the literature. Despite the presence of main environmental effects, there was no evidence of effect modification by genotype status. Additional replication efforts to measure G by E are needed to better understand the origins of mental health and illness, especially in LMIC. (Contains 1 table and 2 figures.)

Background: Attention-deficit/hyperactivity disorder (ADHD) symptoms are dimensionally distributed in the population. This study aimed to assess the role of the catechol-O-methyltransferase (COMT) and of the dopamine transporter (DAT1) genes on ADHD symptoms in the general population. Methods: We investigated 4101 individuals from the 1993 Pelotas Birth Cohort Study using the parent version of the Strengths and Difficulties Questionnaire (SDQ) at ages 11 and 15 years. The SDQ hyperactivity/inattention scores were the main outcomes. Results: Linear regression analyses demonstrated that the increasing number of [COMT.sup.158]Val and DAT1 10R alleles significantly predicted increasing SDQ hyperactivity/inattention scores in boys at both 11 and 15 years of age ([beta] coefficient = 0.049, t = 2.189, p = 0.029, [R.sup.2] = 0.012, and [beta] coefficient = 0.064, t = 2.832, p = 0.005, [R.sup.2] = 0.008, respectively). The presence of both [COMT.sup.158]Val and DAT1 10R alleles was also associated with full categorical ADHD diagnosis at 18 years of age in boys ([chi square] = 4.561, p = 0.033, odds ratio 2.473, 95% confidence interval 1.048-5.838) from this cohort. We did not observe these associations in girls. Limitations: Our analyses of SDQ hyperactivity/inattention scores were not corrected for SDQ scores of conduct problems because these variables were highly correlated. Conclusion: This study demonstrates a role for COMT and DAT1 genes on hyperactivity/inattention symptoms and provides further support for ADHD as the extreme of traits that vary in the population. It also confirms previous evidence for sexual dimorphism on COMT and DAT1 gene expression., Introduction Symptoms of hyperactivity/impulsivity and inattention are dimensionally distributed in the population. Evidence supporting this idea comes from the study of twin pairs from the general population, which demonstrate high [...]

Background: All previous longitudinal community studies assessing the continuity of child behavioral/emotional problems were conducted in developed countries. Method: Six hundred and one children randomly selected from a Brazilian birth cohort were evaluated for behavioral/emotional problems through mother interview at 4 and 12 years with the same standard procedure--Child Behavior Checklist (CBCL). Results: CBCL Total Problem score presented a "medium" stability (r = 0.42) with externalizing problems showing higher stability and more homotypic continuity than internalizing problems. Of the children presenting deviant scores at the age of 4, only 31% remained deviant at the age of 12 (p less than 0.001). A "deviant" CBCL Total Problem score at 12 years old was predicted by Rule-Breaking Behavior [OR = 7.46, 95% CI 2.76-20.19] and Social Problems [OR = 3.56, 95% CI 1.36-9.30] scores at 4 years of age. Either Rule-Breaking or Aggressive Behavior--externalizing syndromes--were part of the predictors for the three broad-band CBCL scores and six out of the eight CBCL syndromes. Conclusions: Behavioral/emotional problems in preschool children persist moderately up to pre-adolescence in a community sample. Externalizing problems at the age of 4 comprise the developmental history of most behavioral/emotional problems at pre-adolescence. Our findings concur with findings from developed countries and are quite similar for continuity, stability and predictability.

Based on Bronfenbrenner's (1999) ecological perspective, a longitudinal, prospective model of individual differences in the quality of home environment (Home Observation for Measurement of the Environment--HOME) was tested in a sample of 179 Brazilian children and their families. Perinatal measures of family socioeconomic status (SES) and child birth weight had direct effects on HOME at preschool age. As either family SES or child birth weight increased, HOME also increased through diminished emotional distress in the mother a month following childbirth. SES had a negative effect on number of children in the household, which in turn had a long-term negative impact on HOME. Compared to mothers who had reported not to plan their pregnancy, those who did were more likely to have fewer children, to report more spouse support during childbearing, and to show less emotional distress a month after childbirth, all of which also influenced HOME at preschool age. These findings are discussed in light of the broader socio-ecological Brazilian context, with direct implications to clinical practice aimed at improving the quality of home environment.

Background: This investigation aimed at examining, through an epidemiological study, the social demographic, family and individual determinants of behaviour problems in preschool children. Method: Six hundred and thirty-four children, age four years, and their mothers, belonging to a cohort of 5,304 children being followed from birth, took part in the study. During a home visit, the child's behaviour problems and IQ were examined, as well as the prevalence of maternal psychiatric disorder, the quality of the home environment, and other social demographic, family and individual factors. Results: The results revealed a prevalence of children's behaviour problems of 24% (clinical and borderline groups). Regression analysis showed that maternal psychiatric disorder, education and age, number of younger siblings and quality of the home environment explained 28% of the variance of the child's behaviour problems. Conclusions: The results point to the multi-determination of child behaviour problems.

Background: Population studies have suggested that most adults with attention-deficit hyperactivity disorder (ADHD) did not have the disorder in childhood, challenging the neurodevelopmental conceptualisation of ADHD. Arbitrary definitions of age at onset and lack of defined trajectories were accounted for the findings.Aims: The objective of this study was to assess the proportion of individuals presenting with either a neurodevelopmental trajectory or late-onset disorder, and to assess risk factors associated with them.Method: Data of 4676 individuals from the 1993 Pelotas birth cohort at 11, 15, 18 and 22 years of age were used. Polythetic and latent class mixed model analyses were performed to define ADHD trajectories from childhood to adulthood, and characterise the neurodevelopmental or late-onset courses. Regression models were applied to assess factors associated with different trajectories.Results: Classical polythetic analyses showed that 67% of those with ADHD at 22 years of age had a neurodevelopmental course of the disorder. Latent class mixed model analysis indicated that 78% of adults with ADHD had a trajectory of persistent symptoms, more common in males. The remaining adults with ADHD had an ascending symptom trajectory that occurred after puberty, with late-onset ADHD associated with female gender and higher IQ.Conclusions: Both polythetic and latent trajectories analyses provided empirical evidence supporting that the large majority of adults with ADHD had a neurodevelopmental disorder. [ABSTRACT FROM AUTHOR]