Depression after Surgery? Is this a normal thing?

Hi guys. I had my last step today in the progress towards my surgeon submitting my request for surgery. It was the psych eval. I understand that I need to have realistic expectations,( and I feel that I do) for after but the psychiatrist kept going on about depression after surgery. I had post partum depression after my third daughter was born( long bed rest, husband deployed, three kids, I think I should have had it) and she is concerned that I will have depression issues after the surgery. At first that did not make sense to me because this surgery is going to help me to feel and look better. So my question to you all is did any of you ever have this and if so does it last long? I am glad that I had this consult , she was making sure that I understood what I was signing on for, that this is not reversible, that I have to make major every day life changes. So I feel that I am ready, but I just want to know a little more about the depression thing. Thanks again, for all the info that I have gained from you all, and I promise to stop pestering with questions. Thanks, Cindy