A vibrating pill could help doctors determine if a patient with anorexia nervosa may have a higher risk of relapse, according to a new study by UCLA Health.
Anorexia nervosa is a psychiatric disorder characterized by persistent restriction of food intake, fear of gaining weight and distorted body image, often leading to significantly low body weight. Relapse rates for people treated for the disorder are alarmingly high at up to 50% within one year of the person restoring their body weight. The disorder has one of the highest mortality rates of any psychiatric disorder, with suicide being the leading cause of death.
Although restoring body weight is a central goal of treatment, many patients continue to struggle after reaching a healthy weight. However, the mechanisms underlying the disorder are not well understood, and there is a lack of objective biomarkers to help doctors track how a patient responds to treatment.
In a study published in JAMA Psychiatry, UCLA researchers used an ingestible, vibrating capsule that not only helped to predict the risk of relapse but also shed new light on how the disorder affects the nervous system.
"People with anorexia nervosa do not simply ignore signals from the body," said the study's senior author Dr. Sahib Khalsa, psychiatrist and neuroscientist who serves as Director of Anxiety Disorders Research and Associate Professor in Residence at the UCLA Semel Institute for Neuroscience and Human Behavior. "Rather, their nervous system may process gut sensations differently, making those signals harder to detect, trust and learn from. Over time, that may contribute to the persistence of symptoms even after weight is restored."
Khalsa and his team recruited 62 women and girls hospitalized with anorexia nervosa whose weight had been restored to healthy levels and 57 healthy controls. The participants swallowed a vibrating capsule that researchers could remotely control to produce gentle vibrating sensations of varying intensity in the stomach. During the experiment, participants were asked to press a button whenever they felt a vibration. Researchers simultaneously monitored brain, heart and stomach rhythm activity. Participants also self-reported hunger levels and other bodily sensations. Researchers then performed follow-up evaluations with the anorexia nervosa participants for six months after hospital discharge.
The data were analyzed using a computational model designed to estimate how strongly participants expected to feel stomach sensations, how much their brains relied on incoming bodily signals and how quickly they updated their expectations when signals were present or absent.
Compared with healthy individuals, anorexia nervosa participants were less accurate at detecting subtle stomach sensations, more likely to believe that no sensation was occurring even when the pill was vibrating, and slower to revise those expectations when stomach signals were present.
"In essence, some individuals with anorexia nervosa appeared to enter the task expecting not to feel signals from the gut and were less likely to update those expectations when signals occurred," Khalsa said.
Several of these gut-brain measures were associated with relapse risk during the six-month follow-up period. Anorexia nervosa participants whose perception was especially biased toward ignoring gut signals were more likely to relapse.
"One of the most striking findings was that these differences persisted even after weight restoration," Khalsa said. "Recovery from anorexia nervosa isn't just about restoring body weight. The underlying brain-body communication problems may remain and could contribute to relapse."
Khalsa said these gut-brain measures could eventually serve as biomarkers that can help doctors to identify patients at higher risk of relapse and track whether treatments are improving how the brain processes bodily signals.
The researchers noted the findings need to be replicated in broader and more diverse populations before firm conclusions can be drawn.
