Table 1 presents the characteristics of the 14 studies that were included in the meta-analyses. There were a total of 14 250 participants of whom 1769 were classified as having depression, and 12 481 did not have depression. Published data were used from 4 studies and original data were used from 10 studies. There was wide variation in the demographic characteristics (eg, proportion of women, age distribution) and sample sizes, which ranged from 118 to 4175 participants. Most of the participants were white except for a multiethnic sample in one study26 and an Asian sample in another study.30 Genotype distributions were similar among white participants; however, Asian individuals had higher S allele frequency than white individuals. Nine of the studies used a structured interview to assess either DSM-IV or ICD-10 major depression,10,15,17,19,25,27,30-32 whereas the other 5 assessed depressive symptoms via self-rated symptoms scales.16,18,20,23,26 Stressful life events measures were assessed consistently across most of the studies using the Brugha List of Threatening Experiences,42,43 whereas a few studies included measures of somatic illness, unemployment, and social stressors. The final column of Table 1 describes whether the findings replicated those of Caspi et al.10
