Furthermore, while our targeted gene and transcription factor binding profile is key to implicating molecular regulation of the HTR2A in relapse-related behaviors in cocaine-dependent individuals, it is wholly conceivable that an unidentified gene by environment interaction and/or the highly polygenic nature of psychiatric disorders exists, such that the methylation profile of the HTR2A may aggregate with an unidentified genetic/epigenetic target to contribute to phenotypic variation (74, 75). The gene discussed is HTR2A; the disease is psychiatric disorder.