Can Positive Parental Reinforcement Counter Genetic Risk for Callous-Unemotional Behavior?

Conduct problems are a common reason for a childhood referral tomental health and educational services and represent a substantial public health cost (1). Callous-unemotional behaviors, indicative of lack of empathy and remorse, characterize children who are at risk of developing persistent conduct problems (2). Previous research indicates that callousunemotional behaviors are moderately to highly heritable (3) and that conduct problems that co-occur with high levels of callous-unemotional behaviors may be more heritable than conduct problems that do not co-occur with these behaviors (4). In other words, children with conduct problems and callous-unemotional behaviorsmaybe genetically vulnerable to developing persistent antisocial behavior. However, for complex behaviors genetic vulnerability does not equal destiny for developing a particular outcome; there are no genes that directly code for callous-unemotional behavior. Genes code for proteins that influence characteristics such as neurocognitive vulnerabilities that may in turn increase risk for developing callous-unemotional behaviors and conduct problems. Although an individual’s genome likely limits a “range for phenotypic expression” (so-called reaction norm), it does not prespecify how an individual will turn out. The specific developmental trajectory of any individual is determined by a complex interplay between genetic propensities and other factors that constrain how those genetic propensities are expressed at different levels of analysis, and throughout different developmental stages. Genetic variants that are associated with callous-unemotional behaviors (once they are reliably ascertained) are likely to confer advantages as well as disadvantages, depending on the environmental context. The challenge for researchers and practitioners alike is to uncover themechanisms throughwhich individuals with different genetic and environmental vulnerabilities arrive at maladaptive or better-adjusted outcomes. Parenting may represent one of these mechanisms. Harsh and negative parenting has been associated with higher levels of callous-unemotional behaviors, whereas a warm parental style has been associated with lower levels of callous-unemotionalbehaviors inchildren(5). But it isnotselfevident that such parenting correlates of callous-unemotional behaviors reflect purely environmental causal influences of parenting on behavioral development. Parents with genetic risk factors for antisocial behavior are likely to display parenting behaviors in linewith these risks (e.g., harsh parenting) and also pass these genetic risk factors, which are likely to influence conduct problems and callous-unemotional behaviors, to their offspring. This means that part of the association between less than optimal parenting strategies and conduct problems/callous-unemotional behaviors may represent a genetic confounder (passive gene-environment correlation), which has been demonstrated for antisocial behavior (6). We also know that children with conduct problems and callousunemotional behaviors are extremely challenging to parent. They typically show diminished empathy for others, display less remorse, manipulate others, and do not seem to want to please adults or readily showaffection to others. It is therefore likely that the parenting reactions they evoke are different from those that less challenging children evoke, and recent research suggests that this is the case (7) (evocative gene-environment correlation). To date, only two genetically informative longitudinal studies have investigated parenting and development of callousunemotional behaviors (8,9). Results fromthefirst of these studies, capitalizing on amonozygotic twin differences design, suggest that the association between harsh and negative parenting and higher levels of callous-unemotional behaviors in children may, at least in part, reflect genetic vulnerability within families (8). This could reflect either a shared genetic vulnerability for poor parenting and callousunemotional behaviors or an effect of callous-unemotional behaviors in evoking negative or harsh parenting. Complementing and extending this work, a highly informative and exciting adoption study by Hyde and colleagues in this issue of the Journal (9) demonstrates both the impact of biological risk for conduct problems and callousunemotional behaviors anda clear indication that protective environmental factors are able to moderate the expression of that risk. In the Hyde et al. study, a total of 561 adopted children and their adoptive and biological families from the Early Growth and Development Study were assessed longitudinally. Adopted children were assessed on callousunemotional, oppositional, and attention-deficit behaviors Thesefindings areextremely encouraging, as the biological risk for early callous-unemotional behaviors appeared to be completely buffered by positive reinforcement from the adoptive mother.