Eating disorders may be due to an impairment in endocannabinoid signalling [295] as evidenced by an upregulation of CB1R mRNA in the blood of patients with anorexia nervosa and bulimia nervosa [295], and significant reduction in body weight loss and running wheel activity in an activity-based anorexia (ABA) rodent model after administration of CB1R/CB2R agonist Δ9-THC [296,297] and the synthetic CB1R/CB2R agonist, CP-55,940 [296]. This evidence concerns the gene CNR1 and anorexia nervosa.