Multiple chemical sensitivity can indeed either cause or exacerbate the symptoms of depression. The isolation it puts on the person suffering with it is difficult to deal with. Many people lose their support systems because they can't be around people due to the triggers contained in fragrances, new buildings, and even in the environment itself. If you don't have good coping mechanisms and a strong support system, it can feel like you're all alone. having to limit your interaction with other people, where you go, how long you can stay, and those kind of things can be extremely frustrating and cause depression to increase or intensify.