Direct and Indirect Genetic Effects on Aggression.

Background: Family members resemble each other in their propensity for aggression. In twin studies, approximately 50% of the variance in aggression can be explained by genetic influences. However, if there are genotype-environment correlation mechanisms, such as environmental manifestations of parental and sibling genotypes, genetic influences may partly reflect environmental influences. In this study, we investigated the importance of indirect polygenic score (PGS) effects on aggression. Methods: We modeled the effect of PGSs based on 3 genome-wide association studies: early-life aggression, educational attainment, and attention-deficit/hyperactivity disorder (ADHD). The associations with aggression were tested in a within- and between-family design (37,796 measures from 7740 individuals, ages 3-86 years [mean = 14.20 years, SE = 12.03], from 3107 families, 55% female) and in a transmitted/nontransmitted PGS design (42,649 measures from 6653 individuals, ages 3-61 years [mean = 11.81 years, SE = 8.68], from 3024 families, 55% female). All participants are enrolled in the Netherlands Twin Register. Results: We found no evidence for contributions of indirect PGS effects on aggression in either a within- and between-family design or a transmitted/nontransmitted PGS design. Results indicate significant direct effects on aggression for the PGSs based on early-life aggression, educational attainment, and ADHD, although explained variance was low (within- and between-family: early-life aggression R2 = 0.3%, early-life ADHD R2 = 0.6%, educational attainment R2 = 0.7%; transmitted/nontransmitted PGSs: early-life aggression R2 = 0.2%, early-life ADHD R2 = 0.9%, educational attainment R2 = 0.5%). Conclusions: PGSs included in the current study had a direct (but no indirect) effect on aggression, consistent with results of previous twin and family studies. Further research involving other PGSs for aggression and related phenotypes is needed to determine whether this conclusion generalizes to overall genetic influences on aggression.

The Co-Twin Control Design: Implementation and Methodological Considerations.

Establishing causal relationships in observational studies is an important step in research and policy decision making. The association between an exposure and an outcome can be confounded by multiple factors, often making it hard to draw causal conclusions. The co-twin control design (CTCD) is a powerful approach that allows for the investigation of causal effects while controlling for genetic and shared environmental confounding factors. This article introduces the CTCD and offers an overview of analysis methods for binary and continuous outcome and exposure variables. Tools for data simulation are provided, along with practical guidance and accompanying scripts for implementing the CTCD in R, SPSS, and Stata. While the CTCD offers valuable insights into causal inference, it depends on several assumptions that are important when interpreting CTCD results. By presenting a broad overview of the CTCD, this article aims to equip researchers with actionable recommendations and a comprehensive understanding of the design's strengths and limitations.

Continuity of Genetic Risk for Aggressive Behavior Across the Life-Course.

We test whether genetic influences that explain individual differences in aggression in early life also explain individual differences across the life-course. In two cohorts from The Netherlands (N = 13,471) and Australia (N = 5628), polygenic scores (PGSs) were computed based on a genome-wide meta-analysis of childhood/adolescence aggression. In a novel analytic approach, we ran a mixed effects model for each age (Netherlands: 12-70 years, Australia: 16-73 years), with observations at the focus age weighted as 1, and decaying weights for ages further away. We call this approach a 'rolling weights' model. In The Netherlands, the estimated effect of the PGS was relatively similar from age 12 to age 41, and decreased from age 41-70. In Australia, there was a peak in the effect of the PGS around age 40 years. These results are a first indication from a molecular genetics perspective that genetic influences on aggressive behavior that are expressed in childhood continue to play a role later in life.

Family member incarceration and physical health problems: A longitudinal study among Australian households.

This study examines the relationship between poor physical health and exposure to family member incarceration. Longitudinal data (2001-2015) from an Australian nationally representative household-based panel study was used (177,312 observations within 26,572 respondents). Hybrid random-effects models showed a strong correlation between poor physical health and family member imprisonment. However, this strong association can be explained for a large part by differences between individuals, since the association of physical health with within-individual changes in family member imprisonment was considerably lower. Nevertheless, the within-individual analyses showed that male sample members were significantly more likely to experience physical health problems in years in which they experienced family member imprisonment, compared to years in which they did not. This association was not found among females. Moreover, no effect of parental imprisonment on the physical health of young sample members was found.

Big Five Personality Traits of Cybercrime Victims.

The prevalence of cybercrime has increased rapidly over the last decades and has become part of the everyday life of citizens. It is, therefore, of great importance to gain more knowledge on the factors related to an increased or decreased likelihood of becoming a cybercrime victim. The current study adds to the existing body of knowledge using a large representative sample of Dutch individuals (N = 3,648) to study the relationship between cybercrime victimization and the key traits from the Big Five model of personality (i.e., extraversion, agreeableness, conscientiousness, emotional stability, and openness to experience). First, multinomial logistic regression analyses were used to examine the associations between the personality traits and three victim groups, that is, cybercrime victims versus nonvictims, traditional crime victims versus nonvictims, and cybercrime victims versus traditional crime victims. Next, logistic regression analyses were performed to predict victimization of cyber-dependent crimes (i.e., hacking and virus infection) and cyber-enabled crimes (i.e., online intimidation, online consumer fraud, and theft from bank account). The analyses show that personality traits are not specifically associated with cybercrime victimization, but rather with victimization in general. Only those with higher scores on emotional stability were less likely to become a victim of cybercrime than traditional crime. Furthermore, the results indicate that there are little differences between personality traits related to victimization of cyber-enabled and cyber-dependent crimes. Only individuals with higher scores on openness to experience have higher odds of becoming a victim of cyber-enabled crimes.

An Exploration of Mate Similarity for Criminal Offending Behaviors: Results from a Multi-Generation Sample of Dutch Spouses.

There has been a growing body of research examining mate and spousal similarity on antisocial behaviors. The results of these studies have shown varying degrees of similarity between mates and spouses, but the precise mechanisms accounting for such similarity have remained somewhat elusive. The current study builds off this line of research and examines spousal similarity on criminal offending behaviors. Moreover, we also examine the potential factors that might account for spousal similarity. This study analyzed data drawn from two generations of Dutch spouses. The analyses revealed statistically significant associations between mates on criminal offending prior to marriage, a finding that is directly in line with an assortative mating explanation of spousal similarity. In addition, the analyses also revealed that criminal offending between spouses becomes even more similar after marriage, a finding that is line with a behavioral contagion explanation of spousal similarity. We conclude by discussing the limitations of the study along with the implications that these findings have for criminological research.