One observational study including 107 Japanese patients with HIV-1 infection showed that those individuals who carried reduced function variants (*6 and *28) in UGT1A1 had higher median plasma DTG concentrations and were reported to have a significantly higher cumulative incidence of neuropsychiatric adverse events (defined as dizziness, headache, insomnia, restlessness, and anxiety) than those who carried normal alleles in UGT1A1. This evidence concerns the gene UGT1A1 and HIV-1 infection.