Depression tends to suppress immune functioning, resulting in an increase in general post-operative death, more post-operative complications and infections, with longer hospital stays, recovery times and costs.
Depression tends to lower pain tolerance, resulting in higher pain following surgery and in the months or years to follow. Depression increases the risk of post-operative delirium, which may cause for a long and incomplete recovery after surgery.
Depression is associated with lower quality of life following surgery and has a strong association with suicide. Surgical procedures tends to be less effective in those who are moderately depressed and worse, demonstrated in weight loss surgery, spine surgery and coronary artery bypass surgery.