All surgeries involve risk to varying levels.  Some procedures, in particular, involve post-operation follow-up behaviors or activities that can positively or negative affect the effectiveness of the surgery.  One example is bariatric surgery, where a surgeon performs an operation with the intention of helping the patient eventually to lose weight.  Naturally, the patient must follow prescribed guidelines established by the surgeon in order to experience long-term success.  Often, a psychological evaluation precedes the surgeon’s decision to perform the surgery.  This helps him or her to make a prudent determination of how well suited the potential patient would be for the surgery itself—as well as successful after care. Pre-surgery evaluations typically involve a clinical interview, psychological testing, and a review of relevant medical and mental health records.