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.

Levels of MAOA are only one possible piece of the puzzle of better understanding asocial behaviors. Asocial behavior and maltreatment can also be rather subjective to measure: "Antisocial behavior is a complicated phenotype, and each method and data source used to measure it... is characterized by different strengths and limitations" (Caspi et al. 2002: 851). However, even given these limits, the study's findings that 85% of males with a low MAOA genotype who were maltreated engaged in antisocial activities supports the hypothesis that deficits in MAOA can account for different responses to environmental stressors.