Gene-environment interaction and violence manifestation

Interação gene-ambiente e a manifestação da violência

CARTAS AOS EDITORES

Gene-environment interaction and violence manifestation

Interação gene-ambiente e a manifestação da violência

Dear Editor,

It was with great interest that we read the manuscript by Mendlowicz & Figueira about intergenerational transmission of family violence, which is an important subject in times of increasing social violence.¹ Thus we would like to contribute to such debate, approaching the genetic participation and its interaction with environmental factors in the manifestation of this phenomenon.

Until the 80's, most researchers used to believe that abused children were more susceptible to developing violent and antisocial behaviors in the adulthood, showing the importance of environmental components as risk factors for this type of behavior. However, only in the 90's some authors started to investigate the participation of the genetic component as a susceptibility factor for the development of violent and antisocial behaviors. According to these authors, the development of violence would not only be mediated by the environment, however would be the result of the interaction between genetic and environmental factors. In the last five years, some studies have demonstrated that parental antisocial behavior prospectively predicts antisocial behavior in abused children, and that this kind of behavior presents a genetic inheritance. Antisocial violent parents are more likely to abuse their children than parents without such behavior (environmental risk for antisocial behavior in children) and also can transmit increased genetic risk for the development of antisocial behavior.²

In addition, molecular genetic studies have investigated which genes could be involved in the inheritance of antisocial violent behavior, as well as the relation between environmental and genetic factors. For example, Caspi et al. investigated a sample of 1,037 children, with 8% of them presenting history of severe maltreatment.³ Such maltreated children, in an interesting way, more often carried the genotype of monoamine-oxidase type A (MAO-A) gene promoter region, which confers low levels of enzyme expression. Once carrying this low MAO-A activity genotype, the children presented a bigger chance to develop antisocial behavior. Thus, this functional polymorphism in MAO-A gene promoter region could be a risk factor for impulsive behaviors in these children. This could explain why they are more likely to expose themselves to abuse situations, and once abuse occurred, the presence of this polymorphism could contribute to the development of future antisocial traits,² demonstrating the interaction between gene-environment factors for the development of antisocial behavior. Recent meta-analysis has confirmed the association between maltreatment and antisocial behavior in individuals that present the low-MAO-A allele,⁴ suggesting that the MAO-A gene may influence the response to environmental factors, and this biological process may be initiated early in life.⁴ Foley et al., in a large epidemiologic twin study, described that this low-MAO-A active polymorphism was a risk factor for the development of antisocial behavior only in the presence of stressful environmental events, which isolated would not configure a risk factor for this type of behavior.⁵ This finding confirms the importance of the interaction between genetic and environmental factors for the determination of behavioral traits.

Investigations on the genetic component of violence are important to a better comprehension of the mechanism by which trauma and violence in children exerts their effects in the development of antisocial and violent behavior in the adulthood, to help choosing future strategies for their prevention, identifying susceptible individuals.²

Quirino Cordeiro, Jacqueline Siqueira-Roberto, Homero Vallada

Genetics and Pharmacogenetics Program, Department of Psychiatry, Universidade de São Paulo (USP) Medical School, São Paulo (SP), Brazil

References

1. Mendlowicz MV, Figueira I. Intergenerational transmission of family violence: the role of post-traumatic stress disorder. Rev Bras Psiquiatr. 2007;29(1):88-9.

2. Koenen KC. Nature-nurture interplay: genetically informative designs contribute to understanding the effects of trauma and interpersonal violence. J Interpers Violence. 2005;20(4):507-12.

3. Caspi A, McClay J, Moffitt TE, Mill J, Martin J, Craig IW, Taylor A, Poulton R. Role of genotype in the cycle of violence in maltreated children. Science. 2002;297(5582):851-4.

4. Kim-Cohen J, Caspi A, Taylor A, Williams B, Newcombe R, Craig IW, Moffitt TE. MAOA, maltreatment, and gene-environment interaction predicting children's mental health: new evidence and a meta-analysis. Mol Psychiatry. 2006;11(10):903-13.

5. Foley DL, Eaves LJ, Wormley B, Silberg JL, Maes HH, Kuhn J, Riley B. Childhood adversity, monoamine oxidase a genotype, and risk for conduct disorder. Arch Gen Psychiatry. 2004;61(7):738-44.

Financing: None

Conflict of interests: None

Publication Dates

• Publication in this collection
  27 Nov 2007
• Date of issue
  Sept 2007