Aromatherapy, only one of my tools to help with my bipolar depression. I especially use Frankincense, lavender, and lemon balm in my diffusers to help ease depression and anxiety. Besides I like the fragrance it imparts to my house, whether it really helps or not, even the placebo effect is nice.
For more information about essential oils and depression, there are many articles online, I suggest that you look them up or on Pinterest.
This is a photo of my own diffuse. Diffusers are available almost everywhere and in almost every grocery store or health food store. This little diffuser is a USB diffuser I purchased for $26.00