What are the therapeutic properties of limonene in cannabis?

Limonene is a citrus-scented monoterpene found in cannabis strains often marketed as "uplifting" or "energizing." Its pharmacological profile: (1) Anxiolytic/antidepressant: limonene increases serotonin and dopamine levels in the prefrontal cortex and hippocampus in animal models. A small human study found limonene inhalation increased serotonin metabolites. (2) Anti-anxiety: limonene activates adenosine A2A receptors and modulates GABA-A receptors. (3) Immunomodulatory: limonene activates immune cells and has shown anti-tumor effects in breast cancer cell lines and animal models. (4) Gastroprotective: limonene reduces gastric acid secretion and has been used for GERD. (5) Anti-inflammatory: limonene reduces NF-κB activation and pro-inflammatory cytokines. A 2019 clinical study found limonene reduced anxiety in cancer patients undergoing surgery. The evidence base is stronger than for most cannabis terpenes, though still primarily preclinical. Limonene is also found in citrus peel, making dietary exposure common.