Methods for incorporating measures of childhood sexual abuse into genetically informative studies of psychopathology

Childhood sexual abuse (CSA) is associated with childhood and adult-onset psychopathology. We describe some methods of incorporating CSA in twin and molecular genetic studies of psychopathology, drawing from the existing literature and posing future methodological avenues. The classical twin method, using monozygotic (MZ) and dizygotic (DZ) twin data partitions individual differences into genetic, twinshared and individual-specific environmental influences. Within this context, we discuss methods for examining the environmental overlap between CSA and psychopathology and for measuring whether heritable influences on psychopathology vary across individuals exposed and not exposed to CSA. We also review findings from cotwincontrol studies, which allow control for familial background, where authors have demonstrated that the member of a twin pair who has experienced CSA is significantly more likely to also report other psychopathology, when compared to their unexposed cotwin. In addition to methods for assessing unmeasured genotype x measured environmental interactions using twin moderator models, tests of measured genotype x measured environment interaction, with childhood maltreatment as the environmental component, which have underscored the possible role of genotype (e.g. in the monoamine oxidase A gene) on the association between CSA and psychopathology, are also discussed, along with their strengths and caveats. Avenues for future research, including the study of epigenetic change and refinement of measures of CSA are presented.