This study investigated the relationship between the G protein beta3 subunit 825T allele and depression in young, healthy subjects. 825T and 825C allele carriers were characterized among 190 healthy medical students. State depression was assessed by the Becks Depression Inventory, supplemented by subscales of the Freiburg Personality Inventory, and Questionnaire for Measuring Factors of Aggression which assess trait depression. Depression of homo- and heterozygous 825T allele carriers was compared to 825C allele carriers via multi-level statistical analysis. 825T allele carriers displayed higher levels of depression, as measured by each questionnaire. Regression analysis demonstrated that allele type was the single predictor of depression. The predictive capacity of the 825T allele in depression was further supported by odds-ratio analysis. We conclude that the G protein beta3 subunit 825T allele is predictive of depressive mood in a young, healthy population.