HI, thanks for using healthcare magic Smoking suppresses or changes the appetite so the cessation would have played a part in your weight gain but the major effect would be related to diet and activity level. Your depressed mood would understandably decrease your desire to exercise, depression is a serious illness that needs treatment (counselling and medication) Though it does not feel this way at this time, stopping smoking would is a very good thing. This would decrease your risk of a number of diseases. The weight gain would affect your breathing You would need to look at your diet and activity to see if changes would help to lose weight. Your doctor may be able to help with this as well. I hope this helps