The detection of G × E depended upon the absence of CD in six individuals with the low/low MAOA genotype who were also exposed to high levels of childhood adversity. The absence of CD diagnosis in these participants reflects measurement of CD at all waves and does not indicate loss to follow-up. Furthermore, upon inspection of the items used for CD diagnosis, these individuals endorsed items reflecting covert symptoms including lying and truancy rather than overt symptoms such as interpersonal aggression. Therefore, an item response theory approach to measure CD using symptoms to reflect a latent trait rather than a diagnosis is anticipated to have better psychometric properties and improve power to detect G × E (Eaves et al. 2005).
