Our goal is to invite participation from all studies with datasets that have the 5-HTTLPR variant genotyped, and assessments of stress and depression, on at least 300 subjects. We set a minimum study size anticipating that the individuals available for our de novo analyses would typically be only a subset of the study individuals. Setting an arbitrary study minimum was intended to improve the balance between the heterogeneity introduced by a new study and the increased sample size. It also had the potential to ameliorate bias due to a possible publication bias amongst small studies. One drawback to this approach of requiring large sample size is that it may exclude some studies with the most intensive assessments of stress and depression. Invitations were sent to groups that had previously published on the topic. Additional invitations were sent to groups, published or unpublished on this topic, suggested as a potentially qualifying study by a participating group. The goal of this inclusive approach is to minimize the potential impact of publication bias. The participating collaborative studies are listed in Table 1. All
