As part of this special section on genetics and behavioral intervention,
we discuss the papers by McGue et al. and by Davey Smith. In the second half of
our paper, we consider the integration of genetics and intervention research
more broadly.
The two papers describe ways to use genetic controls to infer causation
from correlational (‘observational’) data without intervention.
McGue et al. discuss the use of twins discordant for exposure, which is a
variant of the co-twin control method. This method can show that the link
between an exposure and outcome is not entirely mediated genetically. Davey
Smith discusses a method called Mendelian randomization that
uses DNA to draw causal inferences without the need for experimental
intervention.
Despite the possibilities for using genetic controls to infer causation
from correlational data in order to attenuate the need for intervention studies,
we are most excited about the opportunities for integrating genetics and
intervention research, especially as new DNA technologies make it possible to
incorporate genetics in any intervention research.