This Brain Region May Be the Key To Understanding Different Mental Disorders

Mental health professionals diagnose conditions like depression and schizophrenia after carefully considering someone's behavior. But they can't necessarily tell what's going on in the brain.

However, a recent study from researchers at the University of Cambridge found one brain region that acts similarly across disorders: The left dorsal mid-insula.

The insula was already thought to play a role in self-awareness. Research also shows that the left dorsal mid-insula specifically may help process internal states.

This is part of "interoception," or the ability to sense internal conditions in the body such as pain, hunger, and a need to use the bathroom.

If people with mental disorders such as depression, schizophrenia, and anorexia show common brain activity in this region, it can change the way we understand mental health, Camilla Nord, PhD, lead study author and neuroscientist at the University of Cambridge, tells Verywell.

Different disorders may not be so separate and well-defined, but rather connected. "They're based on something, but there may well not be these clear delineations of clinical groups in the way that we thought," Nord says.

The research was published in The American Journal of Psychiatry in late June, and was supported by NIHR Cambridge Biomedical Research Centre.

Identifying Common Ground

Researchers already know that many with mental health disorders report experiencing physical sensations differently. For example, body image distortion is considered a key symptom of anorexia, while people with anxiety tend to experience more shortness of breath.

To explore brain-body relationships across disorders, Nord and colleagues combined brain imaging data from previous studies, spanning 626 patients with mental health disorders. "We looked at every bit of the brain that was different between a psychiatric group and a non-psychiatric group across all the studies," Nord says.

In the studies, each participant was given an interoception activity while under a brain scanner. Tasks often required them to tune in internally, such as by counting heartbeats, focusing on their stomach or bladder, or receiving mildly painful stimuli.

Nord and colleagues found that the only region that psychiatric patients shared in common, and that differed from participants without these conditions, when doing the activities, was the left dorsal mid-insula. Patients had a range of disorders, including:

• Bipolar disorder
• Anxiety disorder
• Depression
• Anorexia
• Schizophrenia

There might be other regions that are specifically involved in each disorder, Nord says, but the left dorsal mid-insula was the only region in common.

What's Driving This Common Factor?

Nord says a few theories explain why the left dorsal mid-insula could respond similarly across disorders when involved in an interoceptive task.

"One of the most compelling ones thinks that the very state of processing your body differently can make you susceptible to a range of mental health disorders," she says.

Having lived your life experiencing your body as different from others can be a risk factor to developing these disorders. For example, folks with chronic physical conditions show a higher incidence of mental health disorders.

Nord adds that having a physiological difference in the feeling of your body could change your ability to interpret the state of your body too. "That same process is what you're doing when you're interpreting 'Am I unhappy? Am I anxious? Am I seeing reality the way it should be?'"

Although this is hypothetical for now, Nord plans on exploring it in the future. "That ability to be tricked by your own body because your body has physical differences could essentially lead your brain to be more surprised by all of your internal states, including your emotions," she adds.

Should Mental Disorders Be Clearly Defined?

Nord says that two different research trends inspired this study: transdiagnostic approaches and brain-body interactions.

A transdiagnostic approach challenges the idea that mental disorders are neat and tidy packages of symptoms. "It's a perspective that looks at differences in the brain or in behavior that cut across diagnostic categories," she explains.

One way to understand this is by considering how disorders can transform over time. For instance, many are diagnosed with depression and anxiety disorders at different periods throughout their lives.

Comorbidities are also common in other disorders. For example, researchers have found between 47% to 89% of adults with attention-deficit hyperactive disorder (ADHD) also have at least one comorbid disorder, including major depression, substance use disorders, and social phobia.

Nord adds that taking a transdiagnostic approach might allow for direct treatment of specific brain mechanisms. "So you wouldn't say something like, 'We're going to treat depression' anymore," Nord says. "You would say, 'We're going to treat this one thing that happens in the brain in some people with depression, some people with anxiety, some people with psychosis,' and so on."

At the same time, interest in brain-body interactions is growing. "The relationship between physical and mental health runs in both directions," Nord says. "When you suffer from a mental health condition, it's very common to have bodily symptoms," including appetite disruption, pain, and fatigue.

She's interested in why and how mental health and physical symptoms are associated. "One answer is that there are overlapping brain networks between the things that get disrupted in a mental health disorder, and the bits of our brain that we use to process the state of the body."

Implications for Treatment

Considering that no current treatment targets the left dorsal mid-insula, Nord's finding could lead to new interventions.

"My study showed that neither psychological treatment nor antidepressant drugs changed activity in this specific part of the brain," she says. In place of pills, she wants to study whether a brain stimulation to the left dorsal mid-insula could change brain activity and alleviate symptoms.

She'd also like to examine how psychological techniques, such as talk therapy, might change activation in the brain region. "It'd be a way of matching people and treatments," she adds.

One day, researchers could even test potential treatments specifically for disruptions of interoceptive processing. That ability to check-in and evaluate your internal world, Nord adds, can be a key factor to these disorders.

"The brain is all the time trying to predict the world around us," she says. "But it's also trying to predict the world inside us. That's how we mitigate our thirst, hunger. We alleviate negative internal states by predicting them."