Hello Mummy bear.
I will not simply repeat the great posts above by Bain and Mike above but confirm that most people will have some sort of emotional reaction to having this type of surgery. Depression is just one of the miriad of emotions that people can experience and it is often preceded by other emotions such as anger, fear, anxiety, resentment, helplessness and hopelessness and many more, which can sometimes merge into depression to make us feel even worse.
Having a trauma such as this can lead to 'reactive depression' which, research indicates should be treated as soon as possible after the event that brought it on as this makes for a better prognosis.
'Indigenous depression' is the more permanent type that we might have as a personality trait. This tends to be more difficult to treat but be aware that post-surgery, reactive depression can add to indigenous depression with devastating effects.
Medics who train and deal in the physical aspects of illness are often not taught even the rudiments of social, emotional and psychological well-being so they are not necessarily the ones to go to for help and support with regard to mental illness such as depression. Even though the after effects of the operation and the mental trauma are inextricably linked, the treatments are often found in completely different places with different people who have different skill sets.
When and if we cannot work through and control our emotive states by ourselves, it is advisable to seek help from those who know about these things. However beware, because just like on the physical side, there are good and bad practitioners and a whole range in between.
Best wishes
Bill