"There is a high degree of psychopathology in this population, which could influence their ability to make informed consent and/or their reaction to the surgery and subsequent weight loss," said the authors.

The psychological aspect of obesity surgery is little discussed among physicians dealing with obesity or mental health, according to the authors, but it is of increasing relevance as the number of radical surgeries for obesity increases.

In a study of 115 surgical candidates, the American researchers discovered that 70 percent have a current or past psychiatric disorder, including a lifetime prevalence of 56 percent for depressive disorders (compared with 17 percent for the general population). At the time of interview, 17 percent of patients showed evidence of an anxiety disorder.

"These are significant findings," said Elliott Goodman, M.D., surgeon and senior author. "We tend to measure success in terms of weight loss alone. We have neglected to measure outcome in terms of other medical and psychological complications, satisfaction with surgery, nutritional intake, exercise level, measure of self-esteem, interpersonal functioning and work functioning. More studies are needed to further clarify which psychological factors play a role in these outcome variables."