Diet has long been thought to influence our moods. But researchers have discovered that certain foods might actually trigger certain forms of mental illness.

Dr. Joseph Garner, associate professor in the department of animal sciences at Purdue University, studies trichotillomania, a disorder that’s characterized by repetitive hair pulling. Although trichotillomania has been recognized for thousands of years—it has been described in Ancient Greek medical texts—there has been little research done directly on the condition. Doctors know it starts in adolescence and affects between 2 and 4 percent of the population, mainly women.  Treatment options are limited.

Garner and his team hoped to reduce hair pulling behaviors in mice by creating meals high in sugar and tryptophan (an amino acid found in turkey as well as dairy products, soy, tofu and nuts). All the mice were prone to body-focused repetitive behaviors, but only one group were active hair pullers. Instead of getting better, the mice who ate the high-sugar and tryptophan diet got worse.

“The mice that were pulling hair started pulling more hair, mice that weren’t pulling hair began to do so or else began scratching at themselves,” said Garner. The diet triggered the disorder in the healthy (but genetically prone) mice and made those already sick even sicker.

Except for the high levels of tryptophan, the diet’s equivalent in human terms would be one filled with lots of juices, soda and candy—pretty much the average American diet. So does this mean junk food heavy diets could be causing some mental illnesses? Maybe. Garner’s next step is to replicate the study using the same diet excluding the tryptophan. But if he’s right it could mean revolutionary changes in the way we view, and treat, these disorders.

Dr. David Carbonell, psychologist and director of the Anxiety Treatment Center of Chicago, works with people who have trichotillomania. He hadn’t read the study but remains skeptical about the results. “I haven’t seen evidence in anxiety disorders that diet plays a strong role,” he said. Although he welcomes more research into this under-studied disorder, he says cognitive behavioral therapy is the most effective treatment available.