“Major depressive disorder is a devastating psychiatric disease that afflicts up to 17% of the world’s population. Postmortem brain analyses and imaging studies of patients with depression have implicated basal lateral amygdala (BLA) dysfunction in the pathophysiology of depression. However, the circuit and molecular mechanisms through which BLA neurons modulate depressive behavior are largely uncharacterized. Here, in mice, we identified that BLA cholecystokinin (CCK) glutamatergic neurons mediated negative reinforcement via D2 medium spiny neurons (MSNs) in the nucleus accumbens (NAc) and that chronic social defeat selectively potentiated excitatory transmission of the CCK^BLA-D2^NAc circuit in susceptible mice via reduction of presynaptic cannabinoid type-1 receptor (CB₁R). Knockdown of CB₁R in the CCK^BLA-D2^NAc circuit elevated synaptic activity and promoted stress susceptibility. Notably, selective inhibition of the CCK^BLA-D2^NAc circuit or administration of synthetic cannabinoids in the NAc was sufficient to produce antidepressant-like effects. Overall, our studies reveal the circuit and molecular mechanisms of depression.”

https://www.ncbi.nlm.nih.gov/pubmed/30643290

https://www.nature.com/articles/s41591-018-0299-9

“Antidepressant-like effect of delta9-tetrahydrocannabinol and other cannabinoids isolated from Cannabis sativa L. Results of this study show that Delta(9)-THC and other cannabinoids exert antidepressant-like actions, and thus may contribute to the overall mood-elevating properties of cannabis.”  https://www.ncbi.nlm.nih.gov/pubmed/20332000