I can understand that smoking
makes you feel better in your depressed state, but still I would like you to know that smoking can lead to increased intracranial pressure and undermine the benefits of your shunt. Also, it is bad for vision as well, in addition to all other adverse effects you must have heard about. So I would suggest that rather than smoking to feel better, think of other options to improve your mental state. You can consult a psychiatrist
and discuss the possible options which include medications, psychotherapy
or both, as per your requirements and choice.
Hope this has been of help. Best wishes.