Three common mental health disorders share a single brain circuit

Mental health issues like insomnia, depression, and anxiety affect millions, yet their causes remain unclear. These conditions deeply impact sleep, mood, and thinking – and they often occur together.

Someone may face insomnia in youth, anxiety later, and depression afterward. Others experience all three at once. Treatments often offer only temporary relief. Symptoms return, and responses to medication vary. This shows a deeper problem in how we approach mental health.

Overlapping mental health disorders

Scientists now believe that brain function, not just behavior, holds the key. A new study by experts at the Netherlands Institute for Neuroscience explores this idea. The analysis was focused on the brain’s role in these overlapping mental health disorders.

“Insomnia disorder, major depressive disorder and anxiety disorders are the most common mental health conditions, often co-occurring and sharing genetic risk factors, suggesting possible common brain mechanisms,” noted the researchers.

Siemon de Lange, Elleke Tissink, and Eus van Someren worked with experts at Vrije Universiteit in Amsterdam.

The team analyzed brain scans from over 40,000 people in the UK Biobank. Instead of studying genes, they used imaging to find both shared and unique brain patterns.

“In our lab, we explore the similarities and differences between insomnia, anxiety, and depression. Everyone looks at this from a different perspective: some mainly look at genetics and in this study, we look at brain scans,” explained Tissink.

Insomnia, depression, and anxiety

The research team examined several brain features, such as tissue structure and connectivity.

Their findings show that people with any of these three disorders commonly exhibit reduced surface area in the cerebral cortex, smaller thalamic volumes, and weaker connections between different brain regions.

This is significant because these brain characteristics could reflect how symptoms develop and persist.

The shared features support the idea that these disorders might stem from related underlying problems in brain function and development. Recognizing these links is crucial for future treatments.

Each disorder shows distinct brain patterns

Despite the overlap, each disorder shows distinct brain patterns. In insomnia, reduced volume in brain regions tied to reward processing is more evident. This might explain why people with insomnia often lose interest or motivation.

For depression, a thinner cerebral cortex – especially in areas linked to language and emotion – plays a stronger role. This may contribute to the emotional numbness or difficulty in expression often experienced by those with depression.

Anxiety stands out through reduced reactivity in the amygdala and weakened functional connectivity in regions rich in dopamine, glutamate, and histamine. These chemical messengers help regulate mood, attention, and stress response, making their disruption crucial in understanding anxiety.

Mental health disorders share a circuit

“The regions seem separate from each other, but when you map them out together, they all turn out to be part of the same circuit (amygdala–hippocampus–medial prefrontal cortex circuit). So, even though they are distinct areas, they all appear to represent different pieces of vulnerability within the same puzzle,” said Tissink.

This insight points to a shared vulnerability circuit. Understanding this interconnected network could change how treatment is approached.

Instead of addressing each disorder in isolation, therapies could target this broader brain circuit, potentially easing multiple symptoms at once.

Underestimated role of insomnia

Tissink noted that insomnia is often left out of discussions around mental health overlap.

“A lot of research has been done on the overlap between anxiety and depression, but insomnia is often forgotten. This is the first time that we have investigated all three disorders at the same time, on such a big scale,” explained Tissink.

The study emphasizes how often people experience these disorders together – sometimes one after another, sometimes all at once.

Understanding how they connect and interact might explain why treatment for one often helps with another. For example, treating insomnia can also lessen depressive symptoms, but the reason behind this is still unclear.

By focusing on the brain’s structure and function, this research opens new paths. It may lead to better, more holistic treatments and prompt more studies that look at mental health from a whole-brain perspective, rather than dividing it by symptoms.

The study is published in the journal Nature Mental Health.

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