Quetiapine is a second-generation (atypical) antipsychotic agent that exhibits a greater affinity for serotonin 5-HT2A receptors than for dopamine D2 receptors, a characteristic that contributes to its antipsychotic efficacy while minimizing the risk of extrapyramidal side effects and is frequently used for bipolar disorder, schizophrenia, and major depressive disorder. This evidence concerns the gene DRD2 and major depressive disorder.