antisocial phenotypes [1]. Monoamine oxidase A (MAOA), for example, an enzyme that breaks down several monoamine neurotransmitters, has been associated with multiple antisocial phenotypes such as serious physical violence and gang membership [15]. Likewise, low serotonin concentrations (due to the short allele of 5-HTTLPR) have been linked to antisocial and violent behavior [16], [17]. However, candidate studies focusing on the genetic etiology of antisocial phenotypes have generally failed to replicate these genes, a phenomenon observed in genetic studies of other complex traits. For example, Verweij et al (2011), Bosker et al (2010), and Chabris et al (2011) were unable to replicate most of the candidate gene associations for cannabis use, depression, and intelligence [18]–[20]. Publication bias of candidate gene studies is one likely explanation [21].
