An [11C]CURB PET study [54] that investigated fatty acid amide hydrolase (FAAH), an enzyme of the endocannabinoid system that degrades anandamide and thereby indirectly regulates cannabinoid receptor signaling, examined 16 males with ASPD and 16 male control participants (five with schizophrenia). This evidence concerns the gene FAAH and schizophrenia.