Multiple logistic regression analysis showed that probable depressed patients were more likely than those who were not depressed to have had experience of alcohol abuse (OR: 19.03, 95% CI 3.11-375.85; p = 0.0083), and a 100 CD4 cells/mm3 fewer was associated with a 2.9 times increase of the odds of probable depression (95% CI 1.88-4.84; p < 0.0001). The gene discussed is CD4; the disease is major depressive disorder.