Participants were eligible for the study if they were between the ages of 18 and 30, and had a full sibling between the ages of 18 and 30 who was also interested in participating. We opted to recruit siblings rather than other relatives because this approach allowed us to have siblings and probands matched on mean age. We restricted the age of the probands and siblings to 18-30 because we were interested in risk for internalizing psychopathology. It was therefore critical that ‘healthy’ (or low symptom) siblings were not out of the peak risk period for internalizing disorders (through age 45; Kessler et al., 2005 (link)). The premise of examining whether healthy or low-symptom siblings of symptomatic probands have abnormal neural responses is that even though siblings have not developed significant symptoms, they still may carry the vulnerability marker (Zubin & Spring, 1977 (link)). However, if a low symptom sibling was significantly past the peak risk period (e.g., age 50) and still had not developed symptoms, they may be less likely to carry the vulnerability marker, or may even be characterized by some resilience process that counteracted their vulnerability.
Participants were only included in the analyses that follow if complete ERP and self-report data were available from both members of the sibling pair (n = 160). Of these, 10 individuals (from 10 families) were excluded as a result of excessive noise in the ERP data, leaving a final sample of n = 140 individuals, from 70 sibling pairs. The final sample was 59% female, and was racially diverse (43.5% Caucasian-American, 28% Hispanic, 13.4% African-American, 7% Asian, 3.7 % Middle Eastern, 2.4% “Other”, and 2.4 % Mixed Race), well-educated (48.7% had completed at least some college education; 21.5% had completed four years of college) and relatively young (Age M = 22.54, SD = 3.15). All procedures were approved by the University of Illinois–Chicago Institutional Review Board.