Is there something about weight loss surgery that has a negative psychological impact on those who have undergone the procedure?
This seems like a slam dunk. One headline after another in the media is saying just that. Here are a few:
"Attempted Suicide Rises After Weight-Loss Surgery"
"Weight Loss Surgery Increases Risk Of Suicide And Self-Harm, Study Finds"
"Weight Loss Surgery Ends Obesity But Leads To Depression And Suicide"
"Troubled Patients Harm Selves More After Bariatric Surgery"
But, is this true? I have some doubts.
The news reports arose from a study that just appeared in JAMA Surgery Online. The paper was entitled "Self-harm Emergencies After Bariatric Surgery: A Population-Based Cohort Study[.]"
Author Junaid A. Bhatti of the Department of Evaluative Clinical Sciences at the Sunnybrook Research Institute in Toronto, and colleagues from other institutions in the city, studied two matched cohorts.
The first group (control) consisted of 8,815 people mostly women who did not undergo bariatric surgery.
The second group consisted of 8,681 people who did have the surgery.
The scientists compared the difference in the rates of self-harm emergencies mostly suicide attempts in the two groups between during the period between April 2006 and March 2011.
Upon first glance, the headlines look convincing. In both groups combined, there was a total of 158 attempts in 111 people (some people made multiple attempts).
The group that underwent the procedure experienced a self-harm emergency rate of 3.63 events per 1000 patient-years. In the group that did not have the operation, that rate was 2.33 a 54 percent increase.
Yes, the group measured a 54 percent difference, but does this mean that the surgery was responsible? It sure doesn't.
The answer, which is in the abstract, is staring you right in the face: "A total of 147 events (93.0%) occurred in patients diagnosed as having a mental health disorder during the five years before the surgery."
Whoa! Did anyone in the news bother to read even the abstract?? Almost all of the suicide attempts occurred in people who had already suffered from some form of mental health issue. The two most common types are anxiety and depression (they frequently co-exist, and a common view is that they are actually two sides of the same coin).
Here's an alternative headline: "People who are depressed attempt suicide more often that those who are not."
It is possible that bariatric surgery may be responsible for mental disorders later on. But, when the mental health confounder is factored in, it becomes impossible to determine this. The suicide attempts could be arising from the preexisting mental disorder, the surgery, or some combination of both. It is impossible to tell from this study.