Genetics plays a significant role in the behavior that people are displaying; and the studies show that maltreated children may sometimes grow to develop antisocial behavior. It is, therefore, a powerful concern since children suffering from the maltreatment may end up as the delinquents and criminals in their society. The studies on aggression and violence show that behavior is greatly influenced by genetics and heredity. MAO-A is a genetic variant that moderates the level of the effects of maltreating people. The high levels of MAO-A cause a lower probability of violence and aggression in human beings, while low levels of MAO-A cause the increased violence (Caspi et al., 2002).
According to Bremner & Vermetten (2001), stress due to the maltreatment of a child causes the alteration in some neurotransmitter systems that persist through the adulthood and can cause the aggressive behavior. Most neuro chemicals affect and even cause the antisocial or criminal behavior in individuals. This occurrence in body is of the enormous influence from genes and the environment. MAO-A influences on the effect of maltreating children, and this explains why not all maltreated children exhibit some antisocial and violence directed tendencies. The environmental factor that affects or causes violence and aggression is the maltreatment that is a characterization of the maternal stress and the negative family environment. The degree of maltreatment also affects the level of the exhibited antisocial behavior according to the study of Bock & Goode (1996).
The levels of antisocial behavior also differ according to sex of the individual in most of studies done to determine the behavioral relationships between the genes and the environment. The MAO-A genotype is common in X-chromosomes, and this means that a female (with XX chromosomes) has more gene variants. In such case, if a female suffers from the childhood maltreatment of any level, she has more MAO-A genotypes to reduce the effect of maltreatment and violence tendencies. A male (XY) has less MAO-A genotypes, and this deficiency leads to the higher effects of maltreatment of male children, and they are more prone to violence and aggression.