Depression will effect your desire for sexual contact, but with proper therapy, this can be corrected. Two years is an awfully long time for lack of intimacy. You deserve a lot of credit for remaining loyal for that length of time because most men would fail to remain so.

I would suggest going to the Dr with your wife and discussing this with him/her. My doctor often asks me how my love life is and I am very open with him about this. When I was having trouble in the past with intimacy, he changed the dosage and medications that he was prescribing (I was having other issues as well, indicating that the medication wasn't working). If both of you work at it, this can be overcome in time.