It says this about Lemon Oil
Lemon oil's aroma is warming, enhancing and invigorating, and studies have shown it to have antidepressant effects. Lemon apparently has a significant effect on one's ability to concentrate: During a university study in Japan, various essential oils were diffused into an office. When Lemon was diffused, 54% fewer errors were made, with Jasmine Oil, 33% fewer errors, and with Lavender Oil, 20% fewer. Diffusion of essential oils was found to increase test scores by up to 50% when diffused into study and test-taking areas. In addition to its uplifting and clarifying nature, emotionally, lemon is considered an opener of the heart. It is said to alleviate fears of losing oneself, bringing trust and security.