Adolescent IQ Research Articles

Intelligence in youth and health behaviours in middle age

ObjectiveWe investigated the association between intelligence in youth and a range of health-related behaviours in middle age. MethodParticipants were the 5347 men and women who responded to the National Longitudinal Survey of Youth 1979 (NLSY-79) 2012 survey. IQ was recorded with the Armed Forces Qualification Test (AFQT) when participants were aged 15 to 23 years of age. Self-reports on exercise (moderate activity, vigorous activity, and strength training), dietary, smoking, drinking, and oral health behaviours were recorded when participants were in middle age (mean age = 51.7 years). A series of regression analyses tested for an association between IQ in youth and the different health related behaviours in middle age, while adjusting for childhood socio-economic status (SES) and adult SES. ResultsHigher IQ in youth was significantly associated with the following behaviours that are beneficial to health: being more likely to be able to do moderate cardiovascular activity (Odds Ratio, 95% CI) (1.72, 1.35 to 2.20, p < .001) and strength training (1.61, 1.37 to 1.90, p < .001); being less likely to have had a sugary drink in the previous week (0.75, 0.71 to 0.80, p < .001); a lower likelihood of drinking alcohol heavily (0.67, 0.61 to 0.74, p < .001); being less likely to smoke (0.60, 0.56 to 0.65, p < .001); being more likely to floss (1.47, 1.35 to 1.59, p < .001); and being more likely to say they “often” read the nutritional information (1.20, 1.09 to 1.31, p < .001) and ingredients (1.24, 1.12 to 1.36, p < .001) on food packaging compared to always reading them. Higher IQ was also linked with dietary behaviours that may or may not be linked with poorer health outcomes (i.e. being more likely to have skipped a meal (1.10, 1.03 to 1.17, p = .005) and snacked between meals (1.37, 1.26 to 1.50, p < .001) in the previous week). An inverted u-shaped association was also found between IQ and the number of meals skipped per week. Higher IQ was also linked with behaviours that are known to be linked with poorer health (i.e. a higher likelihood of drinking alcohol compared to being abstinent from drinking alcohol (1.58, 1.47 to 1.69, p < .001)). A u-shaped association was found between IQ and the amount of alcohol consumed per week and an inverted u-shaped association was found between IQ and the number of cigarettes smoked a day. Across all outcomes, adjusting for childhood SES tended to attenuate the estimated effect size only slightly. Adjusting for adult SES led to more marked attenuation but statistical significance was maintained in most cases. ConclusionIn the present study, a higher IQ in adolescence was associated with a number of healthier behaviours in middle age. In contrast to these results, a few associations were also identified between higher intelligence and behaviours that may or may not be linked with poor health (i.e. skipping meals and snacking between meals) and with behaviours that are known to be linked with poor health (i.e. drinking alcohol and the number of cigarettes smoked). To explore mechanisms of association, future studies could test for a range of health behaviours as potential mediators between IQ and morbidity or mortality in later life.

MATERNAL SENSITIVITY AND PERFORMANCE AND VERBAL INTELLIGENCE IN LATE CHILDHOOD AND ADOLESCENCE

The aim of this study was to investigate the association between maternal sensitivity and offspring intelligence in late childhood and adolescence. Secondary data (N=117) from the Block and Block (2006a, b) 30-year longitudinal study of Californian children, which began in the late 1960s, was used to test the hypothesis that maternal sensitivity in childhood would be predictive of late childhood and adolescent intelligence. Correlational analyses revealed that maternal sensitivity, as judged by raters viewing mother's interactions with their children in a set of four joint structured cognitive tasks when the child was 5 years of age, was associated with verbal and performance IQ test scores when the children were ages 11 and 18. Using hierarchical regression to control for child sex, socioeconomic status, child temperament, child baseline IQ (as measured at age 4), mother's level of education and mother's emotional nurturance, it was found that the maternal sensitivity and child and adolescent IQ association held for verbal, but not performance IQ. Furthermore, a pattern emerged in which the association between maternal sensitivity and verbal IQ was stronger for adolescents with a lower baseline IQ. The results suggest that maternal sensitivity is associated with offspring verbal intelligence and that this association holds when numerous variables are accounted for. Additionally, this association may be stronger for children with lower IQs.

Association of Childhood Infection With IQ and Adult Nonaffective Psychosis in Swedish Men

Associations between childhood infection, IQ, and adult nonaffective psychosis (NAP) are well established. However, examination of sensitive periods for exposure, effect of familial confounding, and whether IQ provides a link between childhood infection and adult NAP may elucidate pathogenesis of psychosis further. To test the association of childhood infection with IQ and adult NAP, to find whether shared familial confounding explains the infection-NAP and IQ-NAP associations, and to examine whether IQ mediates and/or moderates the childhood infection-NAP association. Population-based longitudinal cohort study using linkage of Swedish national registers. The risk set included all Swedish men born between 1973 and 1992 and conscripted into the military until the end of 2010 (n = 771 698). We included 647 515 participants in the analysis. Hospitalization with any infection from birth to age 13 years. Hospitalization with an International Classification of Diseases diagnosis of NAP until the end of 2011. At conscription around age 18 years, IQ was assessed for all participants. At the end of follow-up, the mean (SD) age of participants was 30.73 (5.3) years. Exposure to infections, particularly in early childhood, was associated with lower IQ (adjusted mean difference for infection at birth to age 1 year: -1.61; 95% CI, -1.74 to -1.47) and with increased risk of adult NAP (adjusted hazard ratio for infection at birth to age 1 year: 1.19; 95% CI, 1.06 to 1.33). There was a linear association between lower premorbid IQ and adult NAP, which persisted after excluding prodromal cases (adjusted hazard ratio per 1-point increase in IQ: 0.976; 95% CI, 0.974 to 0.978). The infection-NAP and IQ-NAP associations were similar in the general population and in full-sibling pairs discordant for exposure. The association between infection and NAP was both moderated (multiplicative, β = .006; SE = 0.002; P = .02 and additive, β = .008; SE = 0.002; P = .001) and mediated (β = .028; SE = 0.002; P < .001) by IQ. Childhood infection had a greater association with NAP risk in the lower, compared with higher, IQ range. Early childhood is a sensitive period for the effects of infection on IQ and NAP. The associations of adult NAP with early-childhood infection and adolescent IQ are not fully explained by shared familial factors and may be causal. Lower premorbid IQ in individuals with psychosis arises from unique environmental factors, such as early-childhood infection. Early-childhood infections may increase the risk of NAP by affecting neurodevelopment and by exaggerating the association of cognitive vulnerability with psychosis.

Association of Playing High School Football With Cognition and Mental Health Later in Life

ImportanceAmerican football is the largest participation sport in US high schools and is a leading cause of concussion among adolescents. Little is known about the long-term cognitive and mental health consequences of exposure to football-related head trauma at the high school level.ObjectiveTo estimate the association of playing high school football with cognitive impairment and depression at 65 years of age.Design, Setting, and ParticipantsA representative sample of male high school students who graduated from high school in Wisconsin in 1957 was studied. In this cohort study using data from the Wisconsin Longitudinal Study, football players were matched between March 1 and July 1, 2017, with controls along several baseline covariates such as adolescent IQ, family background, and educational level. For robustness, 3 versions of the control condition were considered: all controls, those who played a noncollision sport, and those who did not play any sport.ExposuresAthletic participation in high school football.Main Outcomes and MeasuresA composite cognition measure of verbal fluency and memory and attention constructed from results of cognitive assessments administered at 65 years of age. A modified Center for Epidemiological Studies’ Depression Scale score was used to measure depression. Secondary outcomes include results of individual cognitive tests, anger, anxiety, hostility, and heavy use of alcohol.ResultsAmong the 3904 men (mean [SD] age, 64.4 [0.8] years at time of primary outcome measurement) in the study, after matching and model-based covariate adjustment, compared with each control condition, there was no statistically significant harmful association of playing football with a reduced composite cognition score (–0.04 reduction in cognition vs all controls; 97.5% CI, –0.14 to 0.05) or an increased modified Center for Epidemiological Studies’ Depression Scale depression score (–1.75 reduction vs all controls; 97.5% CI, –3.24 to –0.26). After adjustment for multiple testing, playing football did not have a significant adverse association with any of the secondary outcomes, such as the likelihood of heavy alcohol use at 65 years of age (odds ratio, 0.68; 95% CI, 0.32-1.43).Conclusions and RelevanceCognitive and depression outcomes later in life were found to be similar for high school football players and their nonplaying counterparts from mid-1950s in Wisconsin. The risks of playing football today might be different than in the 1950s, but for current athletes, this study provides information on the risk of playing sports today that have a similar risk of head trauma as high school football played in the 1950s.

Household chaos as a context for intergenerational transmission of executive functioning

Executive functioning (EF) may be transmitted across generations such that strengths or deficiencies in parent EF are similarly manifested in the child. The present study examined the contributions of parent EF and impulsivity on adolescent EF, and investigated whether household chaos is an environmental moderator that alters these transmission processes. American adolescents (N = 167, 47% female, 13–14 years old at Time 1) completed behavioral measures of EF and reported household chaos at Time 1 and one year later at Time 2. Parents completed behavioral measures of EF and self-reported impulsivity at Time 1. Results indicated that lower parent EF at Time 1 predicted lower adolescent EF at Time 2 (controlling for adolescent EF and IQ at Time 1), but only in the context of high household chaos. Findings suggest that household chaos may be a risk factor that compounds influences of poor parent EF and compromises adolescent EF development.

How Did Lead Exposure Affect the Children of the '70s?

Lead exposure has been linked to lower IQ in children and adolescents, but effects later in life have not been studied on a large scale.Researchers

Maternal Sensitivity as Measured During Dyadic Cognitive Tasks in Childhood Predicts Verbal IQ in Adolescence

In recent years, human flourishing and its relationship to mental health have attracted significant attention in a wide range of fields. As an interdisciplinary, mixed-methods team with strong roots in critical medical anthropology and critical public health, we are intrigued by the possibility that a focus on flourishing may reinvigorate health research, policy, and clinical care in transformative ways. Yet current proposals to this effect, we contend, must be met with caution. In particular, we call attention to the troubling disconnect between current research on flourishing, on one hand, and the voluminous body of scholarship demonstrating the detrimental impact of structural inequities on health, on the other. We illuminate this blind spot in two ways. We begin with a critical assessment of leading conceptions of flourishing in positive psychology, which are compared to current approaches in the critical social sciences of health. In the second half of the paper, we support our argument by presenting original findings from a mixed-methods study with a diverse sample of interviewees in the Midwestern U.S. city of Cleveland, Ohio (n=167). Our interviewees’ rich narrative accounts, which we analyze both quantitatively and qualitatively, highlight important ways in which everyday understandings of flourishing diverge from prevailing scholarly accounts. Given these gaps and blind spots, now is an opportune time for robust interdisciplinary discussion about the implicit values and presumptions underpinning leading approaches to flourishing and their wide-ranging implications for research, policy, and clinical care in mental health fields and beyond.

Intelligence and early life mortality: Findings from a longitudinal sample of youth

ABSTRACTThe current study examined whether adolescent IQ predicted risk for mortality by the age of 32. Analyses of data from the Add Health revealed that IQ was related to mortality risk, such that respondents with relatively lower IQs were significantly more likely to experience early life mortality when compared to respondents with relatively higher IQs. This association remained statistically significant even after controlling for a host of covariates such as race, gender, involvement in violent behaviors, levels of self-control, and poverty. The average IQ of deceased respondents was approximately 95, whereas the average IQ of living respondents was about 100.

No Effect of Marijuana Use on IQ in Adolescents

Whether marijuana use during adolescence affects cognitive function over time is controversial. To investigate this issue, researchers analyzed data

Are IQ and educational outcomes in teenagers related to their cannabis use? A prospective cohort study

There is much debate about the impact of adolescent cannabis use on intellectual and educational outcomes. We investigated associations between adolescent cannabis use and IQ and educational attainment in a sample of 2235 teenagers from the Avon Longitudinal Study of Parents and Children. By the age of 15, 24% reported having tried cannabis at least once. A series of nested linear regressions was employed, adjusted hierarchically by pre-exposure ability and potential confounds (e.g. cigarette and alcohol use, childhood mental-health symptoms and behavioural problems), to test the relationships between cumulative cannabis use and IQ at the age of 15 and educational performance at the age of 16. After full adjustment, those who had used cannabis ⩾50 times did not differ from never-users on either IQ or educational performance. Adjusting for group differences in cigarette smoking dramatically attenuated the associations between cannabis use and both outcomes, and further analyses demonstrated robust associations between cigarette use and educational outcomes, even with cannabis users excluded. These findings suggest that adolescent cannabis use is not associated with IQ or educational performance once adjustment is made for potential confounds, in particular adolescent cigarette use. Modest cannabis use in teenagers may have less cognitive impact than epidemiological surveys of older cohorts have previously suggested.

The Implications of Unintended Pregnancies for Mental Health in Later Life.

Despite decades of research on unintended pregnancies, we know little about the health implications for the women who experience them. Moreover, no study has examined the implications for women whose pregnancies occurred before Roe v. Wade was decided--nor whether the mental health consequences of these unintended pregnancies continue into later life. Using the Wisconsin Longitudinal Study, a 60-year ongoing survey, we examined associations between unwanted and mistimed pregnancies and mental health in later life, controlling for factors such as early life socioeconomic conditions, adolescent IQ, and personality. We found that in this cohort of mostly married and White women, who completed their pregnancies before the legalization of abortion, unwanted pregnancies were strongly associated with poorer mental health outcomes in later life.

Long-term Outcome in Schizophrenia: a Six-year Follow-up in over 1000 Patients

Background Patients with schizophrenia have lower IQ as compared to the general population. Furthermore, cognitive decline has been observed even before the onset of the first episode psychosis. Whether premorbid functioning and IQ also predict long-term remission status is not yet known. Methods 1057 patients with schizophrenia and related disorders were included in GROUP project. Premorbid Adjustment Scale (PAS), IQ and Positive and Negative Symptom Scale (PANSS) were obtained at inclusion. After 6 years 691 patients were re-examined. On 530 patients we were able to determine remission status using the PANSS remission tool. Patients were divided into two groups; those who were in remission (Rem) and those who were not (NR). Groups were compared on PAS and IQ using independent sample t-tests groups. Results Analyses revealed that patients who dropped out during the follow-up of 6 years had lower IQ, and higher PANSS scores as compared to those who were remained in the study. After 6 years 58% of patients were in remission. Remission status after 6 years was associated with IQ and premorbid adjustment in childhood and adolescence at inclusion. Conclusion Poorer premorbid adjustment and lower IQ at baseline are associated with non-remission after 6 years. This suggests that in order to improve the course and outcome of schizophrenia, one should aim to detect and intervene well before the first psychotic symptoms arise.

IQ and level of alcohol consumption—findings from a national survey of Swedish conscripts.

BackgroundStudies of the association between IQ and alcohol consumption have shown conflicting results. The aim of this study was to investigate the association between IQ test results and alcohol consumption, measured as both total alcohol intake and pattern of alcohol use.MethodsThe study population consists of 49,321 Swedish males born 1949 to 1951 who were conscripted for Swedish military service 1969 to 1970. IQ test results were available from tests performed at conscription. Questionnaires performed at conscription provided data on total alcohol intake (consumed grams of alcohol/wk) and pattern of drinking. Multinomial and binomial logistic regressions were performed on the cross-sectional data to estimate odds ratios (ORs) with 95% confidence intervals (CIs). Adjustments were made for socioeconomic position as a child, psychiatric symptoms and emotional stability, and father's alcohol habits.ResultsWe found an increased OR of 1.20 (1.17 to 1.23) for every step decrease on the stanine scale to be a high consumer versus a light consumer of alcohol. For binge drinking, an increased OR of 1.09 (95% CI = 1.08 to 1.11) was estimated for every step decrease on the stanine scale. Adjustment for confounders attenuated the associations. Also, IQ in adolescence was found to be inversely associated with moderate/high alcohol consumption measured in middle age.ConclusionsWe found that lower results on IQ tests are associated with higher consumption of alcohol measured in terms of both total alcohol intake and binge drinking in Swedish adolescent men.

Особенности полового диморфизма когнитивных способностей и структуры интересов подростков с высоким уровнем интеллекта

We present the results of the study of age dynamics factors of the intellectual abilities of cognitively gifted adolescents, namely manifestations of sexual dimorphism in their intellectual sphere and interests. We described an empirical testing of the hypothesis of the specifics of sexual dimorphism of intellectual abilities of adolescents with a high IQ. The study involved 249 adolescents (St. Petersburg), aged 14-17 years, including 132 adolescent high IQ - 81 girl and 51 boy, 117 adolescents with an average IQ - 66 girls and 51 boy. Intellectual performance (11 faculties - spatial, verbal, math, memory) are measured by the Universal intelligence test, the interests – with a biographical questionnaire. Mathematical processing of data was performed using SPSS Statistics 20. The study showed sexual dimorphism abilities manifested in adolescents with high IQ: girls outperform boys in verbal (p = 0.001), spatial (p = 0.05), mnemonic abilities (p = 0.001) and in general, IQ (r = 0.05); boys outperform girls in mathematical abilities (p = 0.001). No differences were found in adolescents with average IQ. Differences in IQ scores of boys and girls with high IQ were similar to the structure of the differences in their interests. We suggested an especially "sensitive" development abilities of teenagers with a high IQ to the structure of interest.

A closer look at the role of parenting-related influences on verbal intelligence over the life course: Results from an adoption-based research design

The association between family/parenting and offspring IQ remains the matter of debate because of threats related to genetic confounding. The current study is designed to shed some light on this association by examining the influence of parenting influences on adolescent and young adult IQ scores. To do so, a nationally representative sample of youth is analyzed along with a sample of adoptees. The sample of adoptees is able to more fully control for genetic confounding. The results of the study revealed that there is only a marginal and inconsistent influence of parenting on offspring IQ in adolescence and young adulthood. These weak associations were detected in both the nationally representative sample and the adoptee subsample. Sensitivity analyses that focused only on monozygotic twins also revealed no consistent associations between parenting/family measures and verbal intelligence. Taken together, the results of these statistical models indicate that family and parenting characteristics are not significant contributors to variation in IQ scores. The implications of this study are discussed in relation to research examining the effects of family/parenting on offspring IQ scores.

The Implications of High IQ in Early Adolescence for Education, Career, and Adjustment in Midlife: Findings from a Swedish Longitudinal Study

Inquiry into what intellectual talent is and how social institutions can support intellectually talented youth are historic, internationally held concerns. This article provides an introduction to a special issue that deals with the implications of high IQ in early adolescence for several important midlife outcomes. From a societal perspective, it is vital to know the extent to which intellectually talented youth attain an advanced education and become engaged in qualified occupations. Studies in this issue document a diversity of midlife outcomes for a large, reasonably representative urban cohort of intellectually talented Swedish adolescents, as well as consider the importance of gender and social class for these outcomes.

High IQ in Early Adolescence and Career Success in Adulthood: Findings from a Swedish Longitudinal Study

To what extent do intellectually talented adolescents pursue educational and vocational careers that match their intellectual resources? Career outcomes were compared between groups within different IQ ranges with a focus on comparing those with high IQ (top 10%IQ > 119) to those with average IQ. Data were analyzed from the longitudinal Swedish IDA study (N = 1,326) with career outcomes measured in midlife (age 43–47). To obtain at least a master’s degree was almost 10 times more common for those of high IQ than for those of average IQ. Stillthe proportion of high-IQ adolescents who did this was not high (13% of females34% of males) and as much as 20% of them did not even graduate from 3-year high school. For men onlythere was a graded raise in income by IQ group. Within the high-IQ group there was no significant relationship between parents’ socioeconomic status and income. For menhigh IQ predicted a strongly increased income/vocational level in midlife beyond what was predicted from a linear model of the IQ-outcome relationship.

The co-twin methodology and returns to schooling — testing a critical assumption

Twins-based estimates of the return to schooling have featured prominently in the economics of education literature. Their unbiasedness hinges critically on the assumption that within-pair variation in schooling is explained by factors unrelated to wage earning ability. This paper develops a framework for testing this assumption and shows, in a large sample of monozygotic twins, that the twins-based estimated return to schooling falls if adolescent IQ test scores are included in the wage equation. Using birth weight as an alternative proxy for ability yields qualitatively similar results. Our results thus cast doubt on the validity of twins-based estimates.

The Nature and Nurture of High IQ

IQ predicts many measures of life success, as well as trajectories of brain development. Prolonged cortical thickening observed in individuals with high IQ might reflect an extended period of synaptogenesis and high environmental sensitivity or plasticity. We tested this hypothesis by examining the timing of changes in the magnitude of genetic and environmental influences on IQ as a function of IQ score. We found that individuals with high IQ show high environmental influence on IQ into adolescence (resembling younger children), whereas individuals with low IQ show high heritability of IQ in adolescence (resembling adults), a pattern consistent with an extended sensitive period for intellectual development in more-intelligent individuals. The pattern held across a cross-sectional sample of almost 11,000 twin pairs and a longitudinal sample of twins, biological siblings, and adoptive siblings.

Breastfeeding and early white matter development: A cross-sectional study

Does breastfeeding alter early brain development? The prevailing consensus from large epidemiological studies posits that early exclusive breastfeeding is associated with improved measures of IQ and cognitive functioning in later childhood and adolescence. Prior morphometric brain imaging studies support these findings, revealing increased white matter and sub-cortical gray matter volume, and parietal lobe cortical thickness, associated with IQ, in adolescents who were breastfed as infants compared to those who were exclusively formula-fed. Yet it remains unknown when these structural differences first manifest and when developmental differences that predict later performance improvements can be detected. In this study, we used quiet magnetic resonance imaging (MRI) scans to compare measures of white matter microstructure (mcDESPOT measures of myelin water fraction) in 133 healthy children from 10months through 4years of age, who were either exclusively breastfed a minimum of 3months; exclusively formula-fed; or received a mixture of breast milk and formula. We also examined the relationship between breastfeeding duration and white matter microstructure. Breastfed children exhibited increased white matter development in later maturing frontal and association brain regions. Positive relationships between white matter microstructure and breastfeeding duration are also exhibited in several brain regions, that are anatomically consistent with observed improvements in cognitive and behavioral performance measures. While the mechanisms underlying these structural differences remains unclear, our findings provide new insight into the earliest developmental advantages associated with breastfeeding, and support the hypothesis that breast milk constituents promote healthy neural growth and white matter development.