Further complicating our understanding of the dynamics between MAOA uVNTR genotype and the environment are variations in samples and outcome measures. Some samples have emphasized people with psychiatric disorders (Huang et al., 2004; Young et al., 2006), whereas many others represent the wider community. Outcome measures are frequently dichotomous, such as a diagnosis of conduct disorder or antisocial behavior, or a history of violent crime; although continuous measures, such as scores on scales of aggressive behavior or emotional problems, have also been employed. Despite vast heterogeneity in study design, it is worth noting that significant GxE interactions have been identified using both community and case/control populations, using a variety of measures of environmental risk, and with different behavioral outcomes.
