Individuals with major depressive disorder (MDD) who experienced more early-life stress were more likely to test positive for cytomegalovirus (CMV), and this finding was replicated in a confirmation sample despite substantially different inclusion and exclusion criteria. This study tested the hypothesis that early-life stress is a risk factor for CMV infection using a discovery sample of 179 volunteers who were diagnosed with MDD based on the Structured Clinical Interview for DSM-IV, and a replication sample of 295 volunteers who met DSM-V criteria for MDD per the Mini International Neuropsychiatric Interview. Researchers found:

• Among the 474 total participants, 172 (36.3%) had remitted MDD; 152 (32.1%) were taking medication for MDD; and 249 (52.5%) were CMV positive.
• Logistic regression models controlling for age, sex, and ethnicity revealed that individuals with more early-life stress had increased odds of testing positive for CMV in both the discovery (odds ratio [OR], 1.02) and replication (OR, 1.02) samples.
• Participants who affirmed more physical and sexual abuse were more likely to test positive for CMV in both discovery and replication samples.