Twins Study Finds Genetic Cause For Psychopathy

Dr. Essi Viding of the London Kings College Institute of Psychiatry and colleagues have found the tendency toward psychopathic behavior has a strong genetic component. (same press release here)

New research on the origins of antisocial behaviour, published in the Journal of Child Psychology and Psychiatry, suggests that early-onset antisocial behaviour in children with psychopathic tendencies is largely inherited. ... Dr Viding's research looked into the factors that contribute to antisocial behaviour in children with and without psychopathic tendencies. By studying sets of 7-year-old twins, Dr. Viding and her colleagues were able to pinpoint to what extent antisocial behaviour in these two groups was caused by genetic and/or environmental risk factors. A sample of 3687 twin pairs formed the starting point for this research. Teacher ratings for antisocial behaviour and psychopathic tendencies (i.e. lack of empathy and remorse) were used to classify the twins. Those who were in the top 10% of the sample for antisocial behaviour were separated into two groups - those with and without psychopathic tendencies. Following analysis, the results showed that, in children with psychopathic tendencies, antisocial behaviour was strongly inherited. In contrast, the antisocial behaviour of children who did not have psychopathic tendencies was mainly influenced by environmental factors. These findings are in line with previous research showing that children with psychopathic tendencies are at risk to continue their antisocial behaviour and are often resistant to traditional forms of intervention.

For those who recognize the name note that Robert Plomin is one of the co-authors.

Evidence for substantial genetic risk for psychopathy in 7-year-olds (Essi Viding, R. James R. Blair, Terrie E. Moffitt, Robert Plomin) is published in the June 2005 issue of The Journal of Child Psychology and Psychiatry.

The bad kids who feel no remorse are genetically bad.

Preliminary findings from the Twins Early Development Study (TEDS) indicate that within the early-onset group there are at least two etiologically distinct groups of children. Antisocial behavior in 7-year-old children with callous and unemotional traits is under strong genetic influence, whereas antisocial behavior in children without such personality traits is primarily environmentally mediated. Such findings of etiological differences are prompting the search for risk genes, as well as highlighting the need to study environmental risk within a genetic framework. It must be emphasized that high heritability is not equivalent to immutability. Better understanding of gene-environment interactions can come to inform successful prevention programs that target young children. These prevention programs may well be different for etiologically distinct subgroups of children at risk for violent and antisocial outcomes.

Psychopathy is strongly genetically infuenced.

Twin studies can help distinguish between genetic and environmental determinants of violence, said Essi Viding of the Institute of Psychiatry in London. In antisocial 7-year-olds with callous and unemotional traits, Viding found, the antisocial behavior was strongly genetic in origin (a group heritability of 80%). If these youths can be identified early, perhaps with a genetic test on cells from a cheek swab, one could target programs for them. "Genes are not a blueprint that determines outcome," said Viding. "Rather, they act together with other risk or protective factors to increase or reduce the risk of disorder." ... Antisocial behavior and physical violence, it turns out, are moderately heritable. A recent meta-analysis of behavioral genetic studies estimated that 41% of the variance on antisocial behavior is due to genetic factors, about 16% to shared environmental factors, and about 43% to nonshared environmental factors. ... Viding's group is currently trying to find genes associated with callous-unemotional traits. If such genes can be identified, the researchers can explore how environment affects the outcomes of children who carry the genes. For example, they may be able to see whether the same genes place children at risk for both antisocial behavior and hyperactivity. They may also be able to assess how risk genes interact with risk environments throughout development. Genes are not a blueprint that determines outcome. Genes alone are neither sufficient, nor necessary, in causing the antisocial behavior.

I am highly skeptical of claims that genes alone are never sufficient to cause antisocial behavior. Certainly some genotypes make people more at risk of being violent or antisocial only in response to specific types of environmental influences. But surely other genotypes must make other children born "bad to the bone". Claims that environmental interventions can always override genetic influences strike me as denial. Sorry, sometimes the genome wins.

To put my argument another way: Some people are more genetically determined than others. (and I predict people will become more genetically determined in the future) Some people have genes that make them highly susceptible to programming by environmental influences. But others have genes that make them highly resistant to various types of environmental influences. For example, some people are going to be happy or unhappy regardless of their environment. Others will have moods and motivations that are greatly influenced by disappointments or good fortune. Some will become violent as a result of child abuse. Others will stay pacifist no matter how much abuse they suffer.

Also, in some cases where genes make someone highly susceptible to environmental influences the effect is to make that person more prone to become criminal or otherwise problematic for the rest of us. Genes can make a person prone to going down an undesirable developmental path or so prone to antisocial behavior that without taking some rather severe steps to isolate such people from "the slings and arrows of outrageous misfortune" some of them are going to go over to the "dark side of the force". The degree to which they can be triggered by environmental stimuli is so great that the ability of environment to influence them is not a reason for optimism.

Even in cases where one twin becomes a psychopath and the other does not become a psychopath that is not automatic proof that therefore social environment made the difference. Some part of deveopmental outcome is due to random noise. Genes do not perfectly control development. Hardwired differences in brains of twins will be present at birth due to chance. Throw in additional noise in very early childhood and before many social influences are felt genetic and non-genetic but developmentally caused and irreversible (at least with current biotechnology) differences will already be well established.

Genes control the extent to which a person is susceptible to various events in the environment and genes exercise great influence over how a person will respond to abuse as a child or a threat uttered in a bar or other events in a person's life. Genes even control the extent to which developmental outcomes are due to random noise from the environment and from Brownian motion. Hopes that socialization can always compensate for genetic inheritance to prevent antisocial thought patterns and behavior strike me as hopelessly naive.

Once psychopathy as a genetically caused condition becomes accepted and genetic testing and genetic engineering becomes possible do you favor or oppose the use of either genetic testing (for selective abortion) or genetic engineering (perhaps delivered in utero) to prevent the development of psychopaths? Consider your other choices. Early and lifetime institutionalization of kids who are bad to the bone would prevent them from preying on others but conflict with the assumption of "innocent until one has committed a crime", let alone "innocent until proven guilty". The other option is what we do now: let those kids grow up and victimize people before being caught committing crimes. That latter option consigns some people to future victimhood and, worse yet, not all psychopaths are ever caught by the criminal justice system. "Successful psychopaths" with an increased corpus callosum but with a symmetrical hippocampus are much less likely to get caught by the police than psychopaths that also have an asymmetrical hippocampus.

Suppose early environmental conditioning techniques which can reverse psychopathy are discovered. Parentheticaly I'm extremely skeptical of the notion than any socialization practices can counteract the effects of gross differences in brain morphology characteristic of psychopaths. But suppose I'm wrong. Would you favor removing a very young budding psychopath from his parents in order to put him through a social conditioning therapy to reverse his psychopathy?