Given that the endocannabinoid system is known to influence response to stress, mood regulation, level of anxiety and motivation in animals involving a substantial number of behaviors [15, 25, 26, 30–32], in our study design we prioritized behaviors that had greater demonstration in humans, were more specifically related to alterations in available FAAH level and/or more present in MDD. The gene discussed is FAAH; the disease is major depressive disorder.