Examining the effects of dopamine genes on verbal IQ within and between families

Psychopathic Personality Traits and the Successful Criminal

A significant body of literature links psychopathy and psychopathic personality traits with criminal behavior and involvement with the criminal justice system. However, very little research has examined whether psychopathic personality traits are related to being a successful criminal (e.g., evading detection). This study addresses this gap in the literature by examining whether psychopathic personality traits are associated with the likelihood of being processed by the criminal justice system (i.e., arrest). Our findings reveal that psychopathic personality traits are generally not associated with criminal success. Specifically, individuals with high levels of psychopathic personality traits commit more crimes and report more arrests, but they do not seem to have an advantage when it comes to avoiding arrest for the crimes they commit. We discuss the implications of these findings for the psychopathy literature.

Left Parietal Functional Connectivity Mediates the Association Between COMT rs4633 and Verbal Intelligence in Healthy Adults

In Chinese Han population, Catechol-O-methyltransferase gene (COMT) rs4633 is found to be associated with impaired cognitive process. We aimed to investigate the association between COMT rs4633 and verbal intelligence and the underlying neural mechanisms in Chinese Han healthy young adults. In 256 Chinese Han healthy young adults, we explored the modulatory effects of COMT rs4633 on verbal intelligence quotient (VIQ) and functional connectivity density (FCD) of the brain and the mediation effect of FCD on the association between COMT and VIQ. We further investigated the association between the expression patterns of dopamine receptor genes and the effect of COMT on FCD in the human brain. COMT rs4633 TT homozygotes exhibited lower VIQ than CC homozygotes and TC heterozygotes, higher long-range FCD (lrFCD) than CC homozygotes and TC heterozygotes in the left superior frontal gyrus. TT homozygotes and TC heterozygotes showed higher lrFCD than CC homozygotes in the left inferior parietal lobule. The lrFCD differences across genotypic subgroups were negatively associated with the expression of DRD2 and DRD3 genes. The left parietal lrFCD mediated the association between COMT rs4633 and VIQ. These findings provide a biological pathway that COMT rs4633 affects verbal intelligence via modulating the lrFCD of the left inferior parietal lobule.

Examining the influence of adolescent marijuana use on adult intelligence: Further evidence in the causation versus spuriousness debate

OBJECTIVES

There is conflicting evidence regarding the association between adolescent marijuana use and adult intelligence, with some studies suggesting adolescent marijuana use can lead to declines in intelligence. The purpose of this study is to shed additional light on the potential link between marijuana use and changes in intelligence.

METHODS

We employed change scores and ordinary least squares (OLS) analysis to test for associations between marijuana use and changes in intelligence scores from adolescence (ages 12-21) to adulthood (ages 18-26) using data drawn from the National Longitudinal Study of Adolescent to Adult Health.

RESULTS

The findings revealed that while a binary measure of marijuana use (ever/never) maintains a statistically significant association with changes in intelligence scores, the effect sizes are relatively small (β=0.043-0.051). Additionally, our findings did not reveal a significant association between cumulative marijuana use and changes in intelligence scores.

CONCLUSIONS

Taken together, the results suggest that while the binary measure of marijuana use (ever/never) has a statistically significant association with changes in intelligence scores, the binary measure accounts for at most a 1-2 point change in intelligence scores.

Serious fighting-related injuries produce a significant reduction in intelligence

PURPOSE

Fighting-related injuries are common among adolescents within the United States, but how such injuries relate to subsequent cognitive functioning remains unclear. In particular, the long-term effect of fighting-related injuries suffered during important developmental periods, such as adolescence, on subsequent cognitive functioning has been overlooked by previous studies. The purpose of this study is to examine the association between sustaining serious fighting-related injuries and changes in verbal intelligence (IQ) over a 5- to 6-year time period.

METHODS

Longitudinal multivariate statistical models were used to analyze data from the National Longitudinal Study of Adolescent Health collected between 1994 and 2002 and analyzed in 2013.

RESULTS

Even a single fighting-related injury resulted in a significant reduction in IQ over time even after controlling for age, race, sex, and changes in socioeconomic status (SES) over the study period. Additionally, females experienced a significantly greater reduction in IQ from each fighting-related injury than males.

CONCLUSIONS

Fighting-related injuries have a significant impact on subsequent cognitive functioning and intelligence. The implications for future policies and research are discussed in more detail.