It is generally believed that these properties, especially actions at 5-HT2 receptors, are involved in its neuropsychiatric adverse effects (depression, anxiety, hallucinations, aggression, suicidal ideation, and sleep disturbance), as they are alleviated by cyproheptadine, a drug with 5-HT2 receptor antagonist actions [49, 50]. This evidence concerns the gene HTR2A and major depressive disorder.