An animal study has found that bergamot essential oil (BEO) calmed HPA axis activity.[1] While its mechanism of action is not completely understood, BEO may increase the extracellular (outside of the cell) concentrations of some amino-acid neurotransmitters; another animal study found that rats who’d been systemically administered BEO had higher extracellular concentrations of aspartate, glycine and taurine in their hippocampi.[1][2]
Further, some of the specific components of BEO have demonstrated positive properties in isolation. BEO contains linalool (6–15%) and linalyl acetate (23–35%).[3] Linalyl acetate, which is also found in lavender essential oil, has been shown to promote vascular smooth muscle relaxation in animals.[4][5] Linalool has demonstrated anticancer, antimicrobial, anti-inflammatory, antianxiety, antidepressant, and analgesic properties in vitro.
The 5-methoxypsoralen present in cold-pressed BEO may increase plasma melatonin concentrations; melatonin regulates the sleep/wake cycle, which could contribute to the effects of BEO on sleep quality.[4]