3. Type of environmental stressor . Different stressors have been examined for interaction with 5-HTTLPR variation. The most common are broad measures of stressful life events [32,33] and exposure to child maltreatment [34,35]. The method of measurement (self report vs. interviewer), the type of stressors (e.g. chronic vs. acute) and the scale (binary exposed vs. not exposed, frequency as in the original study, or continuous variable) also vary. It has been suggested that the varied methodology in assessing stressful life events in GxE studies may in part explain the inconsistency of findings [18], and in a meta-analysis that differentiated between stressors (child maltreatment, specific stressors, and stressful life events), significant differences between types of stressors were found.
