A total of 57 relevant articles were retrieved from various databases, of which 36 were included after scanning the titles; 21 were removed due to duplication, 18 for irrelevance, 5 for being reviews, and 3 for unavailable data related to the association between 5HT2A T102C and psychological symptoms of Alzheimer's disease and 1 was removed for non-case-control design. The gene discussed is HTR2A; the disease is Alzheimer disease.