AEA has roles in nociception, fear-extinction memory, anxiety, and depression.3, 4FAAH knockout mice have elevated brain concentrations of AEA, display an analgesic phenotype in response to acute thermal stimuli, and show reduced pain in formalin and carrageenan inflammatory models.5, 6 FAAH is therefore an attractive drug target for treating pain, anxiety, and depression, although recent clinical trials with FAAH inhibitors were unsuccessful.7, 8. Here, FAAH is linked to major depressive disorder.