Role of Genotype in the Cycle of Violence in Maltreated Children

Maltreated Children

The role of genotype in the cycle of violence in maltreated children

Caspi, Avshalom, Joseph McClay, Terrie E. Moffitt, Jonathan Mill, Judy Martin, Ian W. Craig,

Alan Taylor & Richie Poulton. (2002). The role of genotype in the cycle of violence in maltreated children. Science, 297: 851-853.

The study "the role of genotype in the cycle of violence in maltreated children" (Caspi et al. 2002) addresses a commonly-observed phenomenon seen in anecdotal experience. Although maltreatment in childhood may seem to predispose some adolescents to act out later in life, not all maltreated children engage in delinquent or criminal behavior. "Maltreatment increases the risk of later criminality by about 50%" (Caspi et al. 2002: 851). The study proposes that certain genetic markers predispose individuals towards criminality while other acted as a buffer against antisocial behavior. "Individual differences at a functional polymorphism in the promoter of the monoamine oxidase A (MAOA) gene were used to characterize genetic susceptibility to maltreatment and to test whether the MAOA gene modifies the influence of maltreatment on children's development of antisocial behavior" (Caspi et al. 2002: 851).

The MAOA gene is responsible for metabolizing the neurotransmitters norepinephrine (NE), serotonin (5-HT), and dopamine (DA). Having enough of these 'feel good' chemicals has been linked to guarding against depression, anxiety, and other mental disorders. In the case of individuals who manifested antisocial tendencies later in life, a deficiency in the MAOA gene was strongly linked to more aggressive behaviors.

But the mechanism of MAOA is more complex than simply causing aggression when there is a deficit of the chemical. Stress itself, not simply genetics, can cause abnormalities in MAOA's impact upon human development. "Maltreatment stress (e.g., maternal deprivation, peer rearing) in early life alters NE, 5-HT, and DA neurotransmitter systems in ways that can persist into adulthood and can influence aggressive behaviors" (Caspi et al. 2002: 851). In other words, while some children may have a natural genetic deficit of MAOA, the brain is not a static entity. With the 'right' (or rather the wrong influences), the anxiety and other maladaptive coping behaviors and aggression characteristic of someone with low levels of MAOA can become manifest in a child who might otherwise have developed more normally, if that child is mistreated.

This study is an illuminating look upon the 'nature vs. nurture' and 'environment vs. genetics debate.' Neither factor can be said to conclusively cause complex behaviors like aggression. Some children are born predisposed to act aggressively and might behave in such a manner, even when treated in a relatively benign fashion by their peers, teachers, and parents. Other children might have such a low amount of MAOA, even in a nurturing and supportive environment they might still have behavior problems. For others, factors in the environment can exacerbate an existing deficit or even cause one, depending on the levels of stress the child was subjected to on a consistent basis.