Weight-loss surgery may have an unintended effect on the brain, possibly increasing the risk of suicidal thinking, alcohol abuse or other “impulse control” disorders, some researchers now believe.

One theory is that surgery may set the stage for a controversial phenomenon known as cross addiction, psychologists say. Studies suggest up to 40 per cent of obese people seeking bariatric surgery could be diagnosed as “food-addicted,” and when a reconfigured stomach makes it impossible for people to eat the way they once did, some might exchange one addiction, for another. “If you take away food,” said Edmonton psychologist Jason Jones, “they’re going to find something else.” Eating, he said, “was just a vehicle for the addiction that’s within them.”

Others believe anatomical and physiological changes resulting from the surgery itself may be at play, including changes to the brain’s reward circuitry.

The case is strongest for alcohol abuse, says Dr. Stephanie Sogg, an assistant professor of psychiatry at Harvard Medical School. The evidence is converging “on a pretty clear conclusion,” she said, “that there is an increased risk of problems with alcohol, specifically after a gastric bypass.”

Sogg, a staff psychologist at the Massachusetts General Hospital Weight Center in Boston, has also seen a handful of cases of compulsive shopping in post-bypass patients, including one case of compulsive shoplifting, as well as compulsive gambling – “mostly in people who already occasionally would get a scratch ticket,” she said, “and now they’re really doing it more compulsively.

There are anecdotal reports of people becoming “addicted” to sex, Sogg said, although she, personally, has seen only one such case.

“These are things I see very, very rarely,” she said. “There’s a hint that maybe there’s something there – but there’s not anything like the kind of consensus that we see in the alcohol.”

Even then, she stressed the risk is small compared with the “vast benefits” the majority of people undergoing bariatric surgery experience.

“It’s important to recognize what some of the complications are and be on the lookout for them and know what to do about them when we see warning signs,” said Sogg, “but not to hesitate in recommending surgery for people who medically really urgently need it.”

More than 6,500 bariatric procedures were performed in Canada in 2013-21014, a fourfold increase over seven years. But people are also getting surgery at private clinics, as well as outside the country.

Two of the most common procedures are Roux-en-Y gastric bypass, which reduces the size of the stomach to about the size of a plum and shortens the intestine, and gastric banding, where a silicone band is looped around the upper part of the stomach, restricting how much people can eat at one time.

Although uncommon, several studies are finding an excess of suicides among patients who have had bariatric surgery.

One possible explanation is that, for a small percentage of patients, surgery might seem their last chance at “fixing their unhappiness,” said Dr. Valerie Taylor, psychiatrist-in-chief at Toronto’s Women’s College Hospital.

“People get wedded to the belief that everything in their life is bad because of their weight,” Taylor said. “Their weight becomes allconsuming, and they think if they can just change their weight, everything is almost magically going to be wonderful,” she said.

“I don’t think someone who is very psychologically healthy before surgery is going to suddenly be contemplating suicide,” Taylor stressed. Studies suggest up to half of bariatric surgery patients have a history of mental illness.

“The best we can do is be very mindful, make sure people are as well as they can be going into surgery and make sure they’re monitored coming out.”

Taylor said there is no evidence to support sexual promiscuity, increased gambling or increased shopping after weight-loss surgery. “It is an urban myth and does not happen,” she said. Problem drinking occurs in people who previously had problems with alcohol, she added.

However, one study published three years ago involving nearly 2,000 patients undergoing weight-loss surgery in the U.S. found the number of people reporting symptoms of alcohol use disorder increased from seven per cent pre-surgery, to 11 per cent post.

Of the patients who started abusing alcohol, half had a history of problem drinking, “and about half are de novo onset cases, which is fascinating,” said Dr. James Mitchell, chairman of the department of psychiatry at the University of North Dakota School of Medicine and one of the study’s authors.

The risk seems to start in the second year after Roux-en-Y bypass – but not gastric banding. Unlike banding, Roux-en-Y permanently rearranges the digestive tract.

After gastric bypass, blood alcohol levels peak earlier and higher, “much higher,” Mitchell said. “People drink a modest amount of alcohol and they’re intoxicated, very rapidly.” The faster a drug works on the brain, the more reinforcing and rewarding the drug is.