A recent Yale study has found that while bariatric surgery — a medical procedure to reduce obesity — improves the moods of the majority of obese patients, it could potentially worsen depression for some.

The study, published in September in the journal Obesity Surgery, examined the possible causes and frequency of depression in patients after bariatric surgery. Though the study concluded that most of the patients’ emotional well-being improved in the months following surgery, the researchers also discovered that a subgroup of the 107 study participants experienced a relative increase in depression six months after the procedure.

“The majority of patients with discernible worsening in mood experienced these mood changes between six and 12 months post-surgery,” said Valentina Ivezaj, associate Yale scientist in psychiatry and the study’s lead author. “We suggest that this may be a key period to assess for depression and associated symptoms following gastric bypass surgery.”

The participants suffering from extreme obesity completed emotional evaluations before the surgery. Six months and then a year after, they completed the same evaluations. The self-reported questionnaires assessed depression, eating disorder behavior, self-esteem and social functioning. The study used these data to produce a numerical BDI — Beck Depression Inventory — rating.

Studies suggest there is ubiquitous stigmatization of obesity in society, which can decrease obese individuals’ overall quality of life, said Yale psychiatry professor John Krystal.

The patients evaluated in the study were mildly depressed prior to surgery on average. But after a year post-surgery, 87 percent of the study participants no longer identified themselves as depressed.

According to Ivezaj, while it is generally true that bariatric surgery minimizes depression in obese patients, it is not always that simple.

The data revealed that 13 percent of patients actually experienced an increase in BDI, while another 13 percent experienced a BDI decrease. Seventy-four percent reported no psychological differences six to 12 months post-surgery. Four percent of patients reported increased depression a year after surgery. Increases in symptoms of depression correlated with higher body mass index and increased incidence of emotional difficulties like low self-esteem and poor social functioning.

Obesity does not just affect the body physically, said Gerard Sanacora, professor of psychiatry at the Yale School of Medicine and director of the Yale Depression Research Program. According to Krystal and Sanacora, obesity has biological underpinnings, which influence an individual’s health, brain function and behavior.

Ivezaj said that she conducted the research in order to dispel the common misconception that bariatric surgery is an easy way out.

“I am inspired by my work with patients who have undergone bariatric surgery,” she said. “In order to be successful following bariatric surgery, patients transform their lives and it takes hard work, determination and dedication to make the required lifestyle changes.”

She said she hoped that the research will help identify individuals with a predilection for depression after bariatric surgery, so that future prevention and intervention implementation might ameliorate the quality of patient life.

Ivezaj said that POWER — the Program for Obesity, Weight and Eating Research — led by Yale School of Medicine professor of psychology and psychiatry and the study’s senior author Carlos Grilo, intends to collaborate with the Yale Bariatric Surgery Program to organize a longitudinal study that will comprehensively assess patients’ eating behaviors, mood, weight and psychological functioning post-bariatric surgery.

According to the Centers for Disease Control, more than a third of American adults are obese.