Chunk #36 — Reasons to be Concerned about the Published cGxE Literature — The Ingredients of cGxE: The Choice of Genetic and Environmental Variables — The Choice of “E”
An equally important issue concerns the choice of E. The challenges within this area are illustrated in the literature examining life stress as an environmental risk factor for depression. In attempting to replicate the original cGxE results of Caspi and colleagues (2003) pertaining to life events, many investigators have incorporated a wide variety of ad hoc measures of life stress (Monroe & Reid, 2008). Almost any form of adversity or challenge, at any time in a person’s life, has been used as an alternative index of “stress.” For example, replication studies on this cGxE topic have included participant life stress occurring over a range of time, from one month through a lifetime. Other studies have adopted life event scales known to possess serious measurement deficiencies (Monroe, 2008), or simply have employed unique measures never used previously. In one review of this literature, only 5 of 18 studies reported psychometric properties of the stress measures (Monroe & Reid, 2008). Finally, even when roughly common omnibus measures of life events were adopted, how the life events were combined (over time, severity, and type) for the final index of stress varied greatly across investigations (Uher & McGuffin, 2010).
