2010

Aims. The aim of the present study was to determine the mediating role of affiliation with cannabis-using peers in the pathways from various dimensions of temperament to lifetime cannabis use, and to determine if these associations also contributed to the development of regular cannabis use. Methods. Objectives were studied using data from 1300 participants of the Tracking Adolescents’ Individual Lives Survey (TRAILS), a large, general population study of Dutch adolescents. We used parent-reports on the Early Adolescent Temperament Questionnaire to assess the dimensions high-intensity pleasure, shyness, fearfulness, frustration, and effortful control at age 10-12. By means of self-reports, lifetime and regular cannabis use were determined at age 15-18, and proportion of substance-using peers was determined at ages 12-15 and 15-18. Models were adjusted for age, sex, intelligence, and parental cannabis use. Results. High-intensity pleasure (OR=1.09, 95%CI=1.05-1.13) and effortful control (OR=0.92, 95%CI=0.89-0.96) affected the risk for lifetime cannabis use through their influence on affiliation with cannabis-using peers. Shyness affected this risk independent from peer cannabis use. Only the pathway from effortful control was additionally associated with the development of regular cannabis use (OR=0.93, 95%CI=0.89-0.98).
Conclusions. Peer cannabis use and, to a lesser extent, certain temperamental characteristics affect an adolescent’s risk of cannabis use, and should be considered in prevention programs. We recommend future research to focus on factors that potentially modify the association between temperament, affiliation with cannabis-using peers and cannabis use.

Objective. Why is low resting heart rate (HR) associated with antisocial behavior (ASB: aggression and rule-breaking) in adolescence? Theory suggests that personality traits mediate this relationship but differently with age. In the present study this age-effect hypothesis is tested; we expected that the relationship between HR and aggression would be mediated in preadolescence by the personality trait behavioral inhibition, but not by sensation seeking. However, the relationship between HR and rule-breaking in adolescence was predicted to be mediated by sensation seeking, but not by behavioral inhibition. Hypotheses were tested separately for boys and girls. Method. HR in supine position was assessed in TRAILS respondents (N = 1752; 48.5% boys) at age 11. Rule-breaking and aggression at age 16 were assessed with two subscales from the Youth Self Report (YSR) questionnaire. Personality (i.e., sensation seeking and behavioral inhibition) was measured at age 11, 13.5, and 16 with the Early Adolescent Temperament Questionnaire-Revised (EATQ-R), Behavioral Inhibition System/ Behavioral Activation System (BIS/BAS) scales, or NEO Personality-Index Revised (NEO-PI-R). Results. In boys, lower HR was associated with aggression and rule-breaking in adolescence. The association between HR and rule-breaking was mediated by sensation seeking in adolescence, but not in preadolescence. Girls’ HR was not associated with ASB and no mediating effects were found. Conclusions. Our findings support the age-effect hypothesis in boys’ rule-breaking behavior. This shows that the association between HR and ASB depends on age, gender, and subtype of ASB.

The purpose was to study how functional polymorphisms in the brain derived neurotrophic factor gene (BDNF val66met) and the serotonin transporter gene linked promotor region (5-HTTLPR) interact with childhood adversities in predicting Effortful Control. Effortful Control refers to the ability to regulate behaviour in a goal directed manner and is an interesting endophenotype for psychopathology because of its heritability and the association of low Effortful Control with both internalizing and externalizing problems. In a longitudinal population-based study Effortful Control was assessed with the parent version of the Early Adolescent Temperament Questionnaire at age 11. Pregnancy and delivery adversities and childhood events were assessed in a parent interview at age 11. Long term difficulties until age 11 were assessed with a parent questionnaire at age 13.5. Blood or buccal cells were collected at age 16 for genotyping the rs6265 and rs25531 SNPs and the 5-HTTLPR length polymorphism. The study included 1032 complete data sets. Effortful Control was significantly predicted by the interaction between BDNF val66met, 5-HTTLPR and childhood events. The BDNF val66met val/val - 5-HTTLPR l’/l’ genotype was unaffected by childhood events, while having either at least one BDNF val66met met or 5-HTTLPR s’ allele (l’/l’-met-carrier; l’/s’-val/val; s’/s’-val/val) made children sensitive to childhood events. Predictions of Effortful Control by pregnancy and delivery adversities and long term difficulties were largely independent of genotype. We concluded that the l’/l’-met-carrier, l’/s’-val/val and the s’/s’-val/val genotypes showed greatest plasticity while the l’/l’-val/val genotype was unaffected by childhood events.

Effortful control is thought to foster adaptive action in defensive contexts, and may thereby protect individuals against anxious inhibition and focus on their own distress. We examined if effortful control predicted adolescents’ perceived arousal, unpleasantness, and control as well as autonomic (HR) and HPA-axis (cortisol) responses during social stress. The data came from a focus sample of TRAILS (TRacking Adolescents’ Individual Lives Survey), a prospective population study of Dutch adolescents (N = 715; mean age 16.11, SD = 0.59; 50.9% girls), who participated in a laboratory session including a social stress task (public speaking and mental arithmetic). Perceived and physiological stress measures were assessed before, during, and after the social stress task. Effortful control was measured using various questionnaires and informants, as well as by means of a reaction time (RT) task assessing response inhibition. Overall, adolescents with high questionnaire-based effortful control tended to feel more relaxed, pleasant, and in control during the laboratory session than adolescents with lower levels of control, and had stronger HR responses to the stress test. Adolescent girls with high inhibitory control as measured by the RT task also had strong HR responses, but inhibitory control was associated with high rather than low perceived arousal. Our results suggest that both questionnaire and RT measures of effortful control predict strong HR responses to challenging situations, but associational patterns diverge with regard to perceived stress measures.