Association between 5-HT receptor gene polymorphism and autism spectrum disorder could not be detected by a transmission disequilibrium study [186], whereas it has been recognized that several antipsychotics used to alleviate aggressive behaviours in autism spectrum disorders, such as aripiprazole, lurasidone, pimozide and risperidone, are 5-HT7 inhibitors [16,187,188,189]. This evidence concerns the gene HTR7 and autism spectrum disorder.