Jean R. Séguin

Executive Functions and Physical Aggression after Controlling for Attention Deficit Hyperactivity Disorder, General Memory, and IQ

This study examined the role of ADHD in the association between physical aggression and two types of executive functions. Boys received a cognitive-neuropsychological test battery over the ages of 13, 14, and 15 years. Diagnostic Interview Schedule for Children (DISC 2.25) data were collected from the boys and one parent between ages 14 and 16, and an IQ estimate was obtained at age 15. Three groups, differing in stability and level of physical aggression since kindergarten, were formed: Stable Aggressive, Unstable Aggressive, and Non-aggressive. Composite scores of validated executive function tests of working memory representing subjective ordering and conditional association learning were formed. A MANCOVA (N = 149) using ADHD status, teacher-rated negative emotionality, general memory abilities, and IQ as covariates was performed on the two composite scores. ADHD and teacher-rated emotionality did not provide significant adjustment to the dependent variables. Number of ADHD symptoms was negatively associated only with general memory and IQ. General memory contributed significantly to adjusting for conditional association test scores. Group differences indicated lower conditional association scores for Unstable Aggressive boys relative to the other groups. Both IQ and general memory abilities interacted with subjective ordering within the groups. Specifically, Stable Aggressive boys performed poorly on this measure and did not benefit from increases in IQ whereas Nonaggressive boys performed best and were not disadvantaged by lower general memory abilities. This suggests a relationship exists between aspects of working memory and a history of physical aggression regardless of ADHD and IQ.

Salivary cortisol and aggression in a population-based longitudinal study of adolescent males

Summary.Chronic antisocial behaviour in youth has been associated with cortisol, a measure of stress reactivity. However, some studies have found low cortisol levels, while others have found elevated cortisol levels. The present study compared variously defined aggressive subgroups for differences in salivary cortisol. A population-based sample of boys was followed longitudinally from childhood to adolescence. Assessments of different forms of antisocial behaviour were obtained from various informants at several points in time, and cortisol was collected at age 13. Higher cortisol levels were found in boys with conduct disorder (CD) than in boys without CD. In addition, boys with an aggressive form of CD had higher cortisol levels than boys who showed a covert form of CD. Furthermore, reactive aggression was strongly correlated with elevated cortisol. Adolescent boys with chronic reactive aggression and those who scored high on aggressive CD symptoms seem to have a more active hypothalamic-pituitary-adrenal system.

Cognitive–Neuropsychological Function in Chronic Physical Aggression and Hyperactivity

Histories of violence and of hyperactivity are both characterized by poor cognitive–neuropsychological function. However, researchers do not know whether these histories combine in additive or interactive ways. The authors tested 303 male young adults from a community sample whose trajectories of teacher-rated physical aggression and motoric hyperactivity from kindergarten to age 15 were well defined. No significant interaction was found. In a 1st model, both histories of problem behavior were independently associated with cognitive–neuropsychological function in most domains. In a 2nd model controlling for IQ, general memory, and test motivation, the 3 working-memory tests (relevant to executive function) remained associated with physical aggression, and 1 remained associated with hyperactivity. These results support an additive model.

Genes, maternal smoking, and the offspring brain and body during adolescence: Design of the Saguenay Youth Study

The search for genes of complex traits is aided by the availability of multiple quantitative phenotypes collected in geographically isolated populations. Here we provide rationale for a large‐scale study of gene‐environment interactions influencing brain and behavior and cardiovascular and metabolic health in adolescence, namely the Saguenay Youth Study (SYS). The SYS is a retrospective study of long‐term consequences of prenatal exposure to maternal cigarette smoking (PEMCS) in which multiple quantitative phenotypes are acquired over five sessions (telephone interview, home, hospital, laboratory, and school). To facilitate the search for genes that modify an individuals response to an in utero environment (i.e. PEMCS), the study is family‐based (adolescent sibships) and is carried out in a relatively geographically isolated population of the Saguenay Lac‐Saint‐Jean (SLSJ) region in Quebec, Canada. DNA is acquired in both biological parents and in adolescent siblings. A genome‐wide scan will be carried out with sib‐pair linkage analyses, and fine mapping of identified loci will be done with family‐based association analyses. Adolescent sibships (12–18 years of age; two or more siblings per family) are recruited in high schools throughout the SLSJ region; only children of French‐Canadian origin are included. Based on a telephone interview, potential participants are classified as exposed or nonexposed prenatally to maternal cigarette smoking; the two groups are matched for the level of maternal education and the attended school. A total of 500 adolescent participants in each group will be recruited and phenotyped. The following types of datasets are collected in all adolescent participants: (1) magnetic resonance images of brain, abdominal fat, and kidneys, (2) standardized and computer‐based neuropsychological tests, (3) hospital‐based cardiovascular, body‐composition and metabolic assessments, and (4) questionnaire‐derived measures (e.g. life habits such as eating and physical activity; drug, alcohol use and delinquency; psychiatric symptoms; personality; home and school environment; academic and vocational attitudes). Parents complete a medical questionnaire, home‐environment questionnaire, a handedness questionnaire, and a questionnaire about their current alcohol and drug use, depression, anxiety, and current and past antisocial behavior. To date, we have fully phenotyped a total of 408 adolescent participants. Here we provide the description of the SYS and, using the initial sample, we present information on ascertainment, demographics of the exposed and nonexposed adolescents and their parents, and the initial MRI‐based assessment of familiality in the brain size and the volumes of grey and white matter. Hum Brain Mapp 2007.

Tryptophan Depletion, Executive Functions, and Disinhibition in Aggressive, Adolescent Males

Low serotonin has been associated with aggressive behavior and impulsivity. Executive functions (cognitive abilities involved in the initiation/maintenance of goal attainment) have also been related to aggression. We tested whether dietary depletion of tryptophan, the amino acid precursor of serotonin, would increase disinhibition (impulsivity) in aggressive male adolescents. Cognitive-neuropsychological variables predictive of disinhibition were explored. Stable aggressive and nonaggressive adolescent men received balanced and tryptophan-depleted amino acid mixtures separately (counterbalanced, double-blind). Commission errors on a go/no-go learning task (i.e., failures to inhibit responding to stimuli associated with punishment/nonreward) measured disinhibition. Aggressive adolescent males made more commission errors as compared to nonaggressives. Lower executive functioning was significantly related to commission errors over and above conventional memory abilities. Tryptophan depletion had no effect on commission errors in the aggressive adolescents, possibly because of a ceiling effect.

Salivary testosterone and aggression, delinquency, and social dominance in a population-based longitudinal study of adolescent males

Testosterone (T) has been found to have a stimulating effect on aggressive behavior in a wide range of vertebrate species. There is also some evidence of a positive relationship in humans, albeit less consistently. In the present study we investigated the relationship between T and aggression, dominance and delinquency over time, covering a period from early adolescence to adulthood. From a large population-based sample (n = 1.161) a subgroup of 96 boys was selected whose behavior had been assessed repeatedly by different informants from age 12 to 21 years, and who had provided multiple T samples over these years of assessment. On the whole, a decrease in aggressive and delinquent behavior was observed in a period in which T rises dramatically. Boys who developed a criminal record, had higher T levels at age 16. In addition, positive associations were observed between T and proactive and reactive aggression and self-reported delinquent behavior. Over the pubertal years different forms of aggressive and delinquent behavior were positively related to T, which may indicate that specific positive links are dependent on the social setting in which this relationship is assessed.

Closing the gap in academic readiness and achievement: the role of early childcare

BACKGROUND Socially disadvantaged children with academic difficulties at school entry are at increased risk for poor health and psychosocial outcomes. Our objective is to test the possibility that participation in childcare--at the population level--could attenuate the gap in academic readiness and achievement between children with and without a social disadvantage (indexed by low levels of maternal education). METHODS A cohort of infants born in the Canadian province of Quebec in 1997/1998 was selected through birth registries and followed annually until 7 years of age (n = 1,863). Children receiving formal childcare (i.e., center-based or non-relative out-of-home) were distinguished from those receiving informal childcare (i.e., relative or nanny). Measures from 4 standardized tests that assessed cognitive school readiness (Lollipop Test for School Readiness), receptive vocabulary (Peabody Picture Vocabulary Test Revised), mathematics (Number Knowledge Test), and reading performance (Kaufman Assessment Battery for children) were administered at 6 and 7 years. RESULTS Children of mothers with low levels of education showed a consistent pattern of lower scores on academic readiness and achievement tests at 6 and 7 years than those of highly educated mothers, unless they received formal childcare. Specifically, among children of mothers with low levels of education, those who received formal childcare obtained higher school readiness (d = 0.87), receptive vocabulary (d = 0.36), reading(d = 0.48) and math achievement scores (d = 0.38; although not significant at 5%) in comparison with those who were cared for by their parents. Childcare participation was not associated with cognitive outcomes among children of mothers with higher levels of education. CONCLUSIONS Public investments in early childcare are increasing in many countries with the intention of reducing cognitive inequalities between disadvantaged and advantaged children. Our findings provide further evidence suggesting that formal childcare could represent a preventative means of attenuating effects of disadvantage on childrens early academic trajectory.

Orbitofrontal Cortex and Drug Use During Adolescence: Role of Prenatal Exposure to Maternal Smoking and BDNF Genotype

CONTEXT Prenatal exposure to maternal cigarette smoking (PEMCS) may affect brain development and behavior in adolescent offspring. OBJECTIVE To evaluate the involvement of the orbitofrontal cortex (OFC) in mediating the relationship between PEMCS and substance use. DESIGN Cross-sectional analyses from the Saguenay Youth Study aimed at evaluating the effects of PEMCS on brain development and behavior among adolescents. Nonexposed adolescents were matched with adolescents exposed prenatally to cigarette smoking by maternal educational level. PARTICIPANTS AND SETTING A French Canadian founder population of the Saguenay-Lac-Saint-Jean region of Quebec, Canada. The behavioral data set included 597 adolescents (275 sibships; 12-18 years of age), half of whom were exposed in utero to maternal cigarette smoking. Analysis of cortical thickness and genotyping were performed using available data from 314 adolescents. MAIN OUTCOME MEASURES The likelihood of substance use was assessed with the Diagnostic Interview Schedule for Children Predictive Scales. The number of different drugs tried by each adolescent was assessed using another questionnaire. Thickness of the OFC was estimated from T1-weighted magnetic resonance images using FreeSurfer software. RESULTS Prenatal exposure to maternal cigarette smoking is associated with an increased likelihood of substance use. Among exposed adolescents, the likelihood of drug experimentation correlates with the degree of OFC thinning. In nonexposed adolescents, the thickness of the OFC increases as a function of the number of drugs tried. The latter effect is moderated by a brain-derived neurotrophic factor (BDNF) genotype (Val66Met). CONCLUSIONS We speculate that PEMCS interferes with the development of the OFC and, in turn, increases the likelihood of drug use among adolescents. In contrast, we suggest that, among nonexposed adolescents, drug experimentation influences the OFC thickness via processes akin to experience-induced plasticity.

Externalizing behavior and the higher order factors of the Big Five.

The comorbidity of various externalizing behaviors stems from a broad predisposition that is strongly genetically determined (R. F. Krueger, B. M. Hicks, C. J. Patrick, S. R. Carlson, W. G. Iacono, & M. McGue, 2002). This finding raises the question of how externalizing behavior is related to broad personality traits that have been identified in normal populations and that also have a genetic component. Using structural equation modeling, the authors applied a hierarchical personality model based on the Big Five and their two higher order factors, Stability (Neuroticism reversed, Agreeableness, and Conscientiousness) and Plasticity (Extraversion and Openness). Cognitive ability was included to separate variance in Openness associated with Extraversion (hypothesized to be positively related to externalizing behavior) from variance in Openness associated with cognitive ability (negatively related to externalizing behavior). This model was used to predict a latent externalizing behavior variable in an adolescent male sample (N = 140) assessed through self- and teacher reports. As hypothesized, externalizing behavior was characterized by low Stability, high Plasticity, and low cognitive ability.

Cohort Profile: The Maternal-Infant Research on Environmental Chemicals Research Platform

BACKGROUND The Maternal-Infant Research on Environmental Chemicals (MIREC) Study was established to obtain Canadian biomonitoring data for pregnant women and their infants, and to examine potential adverse health effects of prenatal exposure to priority environmental chemicals on pregnancy and infant health. METHODS Women were recruited during the first trimester from 10 sites across Canada and were followed through delivery. Questionnaires were administered during pregnancy and post-delivery to collect information on demographics, occupation, life style, medical history, environmental exposures and diet. Information on the pregnancy and the infant was abstracted from medical charts. Maternal blood, urine, hair and breast milk, as well as cord blood and infant meconium, were collected and analysed for an extensive list of environmental biomarkers and nutrients. Additional biospecimens were stored in the studys Biobank. The MIREC Research Platform encompasses the main cohort study, the Biobank and follow-up studies. RESULTS Of the 8716 women approached at early prenatal clinics, 5108 were eligible and 2001 agreed to participate (39%). MIREC participants tended to smoke less (5.9% vs. 10.5%), be older (mean 32.2 vs. 29.4 years) and have a higher education (62.3% vs. 35.1% with a university degree) than women giving birth in Canada. CONCLUSIONS The MIREC Study, while smaller in number of participants than several of the international cohort studies, has one of the most comprehensive datasets on prenatal exposure to multiple environmental chemicals. The biomonitoring data and biological specimen bank will make this research platform a significant resource for examining potential adverse health effects of prenatal exposure to environmental chemicals.