Depression, anxiety and other disorders may have the same genetic cause, study finds

Psychiatric disorders can share common genetic influences, which means parts of DNA can be at the root of more than one mental condition, new research has found.

The study, led by researchers at Texas A&M University and published in Nature, could explain why many mental health conditions occur together, according to a press release.

The researchers examined DNA data for more than one million individuals who had any of 14 childhood and adult-onset psychiatric disorders, and then compared it to data from five million individuals with none of the disorders.

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The disorders were sorted into five groups: compulsive disorders (like OCD and anorexia), schizophrenia and bipolar disorder, neurodevelopmental disorders (such as autism and ADHD), internalizing disorders (depression, anxiety, PTSD), and substance-use disorders.

Each pattern is linked to 238 tiny differences that influence how the brain works and offer clues about why some conditions overlap while others differ. Some traits, like suicidal thoughts and loneliness, were linked to all five patterns.

For the schizophrenia-bipolar group, the strongest genetic links were found in brain cells that send “go” signals and help enable communication between different regions.

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In contrast, internalizing disorders (like depression, anxiety and PTSD) are more strongly linked to cells that help brain signals travel faster, the researchers found.

“By uncovering shared genetic roots, we can start thinking about treatments that target multiple disorders instead of treating each one in isolation,” said co-author John Hettema, M.D., Ph.D., in the release.

The team relied on genome-wide association studies, or GWAS, which compare the DNA of large groups of people with and without a given condition. These studies scan millions of common genetic markers to find tiny differences that are more common in people who have the disorder.

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The researchers then compared each disorder with every other one to see how much their genetic risk overlapped. They did this using a technique called genetic correlation, which reveals whether the same genetic variants contribute to multiple conditions.

‘Another layer of insight’

Dr. Daniel Amen, a psychiatrist, brain imaging doctor and founder of Amen Clinics in California, said the biggest takeaway of the study is that the current method of diagnosing mental illness is “broken because it’s not based on biology.”

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“This new study confirms that mental health disorders share deep genetic connections, especially involving brain development and synaptic function,” Amen, who was not involved in the study, told Fox News Digital.

“What this means is that conditions like depression, bipolar disorder, schizophrenia and ADHD aren’t isolated silos — they’re part of overlapping biological systems that start in the brain, often as early as in utero.”

Amen emphasized that mental illness should be regarded as a brain health issue rather than a collection of psychological symptoms.

“What this study adds is another layer of biological insight, especially for people at risk,” he said. “Eventually, it could lead to screening tools that identify vulnerabilities in childhood, allowing for early interventions before symptoms ever become severe.”

Potential limitations 

The researchers emphasized that genetics alone don’t determine whether someone will have these disorders, just as they don’t determine medical conditions like hypertension and diabetes.

Instead, the genetic traits “set the stage” by increasing or decreasing one’s inherent risk, the authors say, which then can be triggered by other factors, like stress.

“Just because a gene is linked to a disorder doesn’t mean it causes it.”

Amen agreed that “association is not causation,” and that “we’re not yet at the point where doctors can prescribe based solely on genetic profiles.”

“Just because a gene is linked to a disorder doesn’t mean it causes it — or that changing it changes the outcome,” he said. “The environment still matters. Genetics load the gun, but stress, trauma, diet, infections, toxins and head injuries pull the trigger.”

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The brain expert also emphasized the importance of pairing genetic screening with brain imaging.

“If we get this right — and combine genetic research with brain imaging, digital phenotyping and clinical neuroscience — the entire landscape of mental health care will change,” he predicted. “We’ll no longer be diagnosing based on symptoms alone. We’ll be diagnosing based on objective, biological data.”