Mold and other toxins can definitely make you sick, and being sick can make you depressed. Some chemicals can make you depressed, too, or give you other mental/emotional symptoms, including mood swings, dizziness and confusion.
Don't take this lightly, because your remaining ability to function can take a dive without warning. I know, because I got terribly sick more than 20 years ago from multiple chemical exposures, and have been dealing with the consequences ever since. And once I became completely intolerant of certain chemicals, I also started having severe reactions to all molds and mildews, most foods, and other allergens that had never bothered me before. It can be cumulative once your body has been pushed past its limit.
My life is extremely limited now because of all the things I can't do and places I can't go. Like any public place where people are wearing perfume, for instance. Or places / homes / public bathrooms where air "frsheners" are in use. It's a good thing I'm self-employed, because working in a more public situation would be virtually impossible now.
Good luck. You don't really say how big your company is, or even whether you are renting your own office space. But do check out the suggestions here: http://www.presenting.net/sbs/sbs.html#ACTION