Finally, one other critical environmental variable to examine in the context of GXE interactions, in both animal and human models, is stress (for review see Clarke & Schumann, 2009). Recent studies have suggested that exposure to stress has a important impact on the progression of psychopathology, especially during specific developmental periods, and this impact is moderated by genetic factors (Stevens et al., 2009). While there are excellent experimental models of the effects of stress in animals (e.g., Heilig & Koob, 2007) and in humans (Greeley & Oei, 1999; Sher, 1987; Sher & Grekin, 2007), it is important to note that the intensity and duration of stressors that can be ethically administered to human participants in the laboratory is limited, thus, restricting our ability to examine traumatic stress exposures in the laboratory. Consequently, the examination of gene x stress interactions may be largely limited to retrospective/observational studies in humans if severe or traumatic stress is the target of inquiry. (Although in recent years electronic diaries and ecological momentary assessment have been used to study alcohol/stress interactions in “real time” in the
