Comorbid psychiatric illnesses, including depression, are common in HIV-infected patients.[34] The prevalence of depression in HIV-infected clinic populations has ranged from 22% to 38%.[34, 35] Younger age, unemployment, lack of health insurance, low CD4+ cell counts, HIV-related symptoms, not having a partner, poor quality of social support, and use of noninjection drugs were significant predictors of depression in one study.[36] Patients with HIV infection who are older than 35 years are more likely to suffer from depression, anxiety, confusion, and fatigue. This evidence concerns the gene CD4 and major depressive disorder.