We noted that chronic (7–10 days) THC treatment in vivo eliminates LTD and CB1 agonist-induced depression in both young and adult mice, but LTD and CB1 agonist-induced depression are still present after a single exposure to THC in both age groups (Friend et al. 2017; Ostlund et al. 2022). The gene discussed is CNR1; the disease is major depressive disorder.