Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. If peppermint oil would benefit depression or anxiety either orally or in a diffuser. My advice to you is to look for more evidence based treatments such as the use of the herb lemon balm for anxiety. Peppermint oil is used primarily for the relief of headaches or in an enteric coated pill for dyspepsia. A review of the literature shows no evidence based use of peppermint for the relief of depression or anxiety. Depression medications that once worked often do not work anymore after some time on them and a change in the type of medication is indicated. Natural methods of depression control can be explored such as making sure the thyroid is functioning properly, that you are not deficient in vitamin D or the omega 3 fatty acid. Depression is an underdiagnosed and undertreated disorder with nutrition frequently ignored. I advise that you in addition to the recommendations above begin to eat your meals in a social situation with more fresh fruits and vegetables, avoid sugar and all added sugars, increase you intake of seafoods/seaweeds and switch to only whole grains instead of white breads/flour. Remember to keep hydrated as you increase your fiber intake so elimination is not affected, adequate elimination being an important part of mood control. As far as aromatherapy goes, stimulate your environment with sandalwood or jasmine for control of depression. Avoid the synthetic oils use only natural and avoid additives. The mechanism of action is multifaceted - it puts you in the moment, creates an environment conducive to meditation or conditioning and promotes a feeling of calmness by interacting with the sensory neurons in your nose and brain. Please do not feel alone. Many suffer with depression. You can lift that cloud. do not give up. Hope I have answered your query. Let me know if I can assist you further.